Vayne is a powerhouse in Dominion. She has amazing synchronizing ability with the newer items, and her 1v1 potential with DPS makes her dangerous to any and everything on the Crystal Scar. So, that being said, here is a guide that explains how I play Vayne on Dominon coupled with the build I use.
I choose Greater Mark of Desolation because Vayne's usefulness in Dominion is dependent on her ability to do a lot of damage. And while she is capable of doing a lot of damage without any armor penetration thanks to Silver Bolts, it only procs every 3 attacks, and I would rather do consistent damage for every attack. That's not saying that armor pen is the only way to go though. Greater Mark of Attack Speed will allow you to get more early game Silver Bolts procs, which can be devastating. The reason I don't get these however is because of the large amount of Attack Speed items I get in my build.
Seals: I like Greater Seal of Armor. There are tons of viable choices here, but thanks to Dominion's aura, I don't really like getting anything for mana regeneration and Greater Seal of Evasion don't really give a large enough bonus to be worthwhile by themselves.
Glyhs: I chose Greater Glyph of Cooldown Reduction because this to me seems like the best choice of a glyph for Vayne. I've seen a lot of builds prioritize attack speed here, which may be useful in Summoner's Rift where you need something to carry you until you get the gold necessary to buy attack speed, however in Dominion, you get enough gold to make the marginal gain from Greater Glyph of Attack Speed negligible. Another viable choice of Glyphs, if you're looking for a little tankier build, is to get Greater Glyph of Magic Resist for a little bit more MR.
Quintessences: I chose Greater Quintessence of Attack Speed because of the early game attack bonus. This is much more viable in Dominion with Vayne because you start the game with your Silver Bolts, making attack speed early game much more profitable. Another choice would be Greater Quintessence of Desolation. I don't use these in Dominion however because of the aura from the Crystal Scar which gives me 15% armor penetration anyway. So while a smaller amount of flat penetration, like from your marks, is nice; I would rather get the attack speed for these. Although, I will say, it would also be extremely viable to exchange the Marks with the Quintessences. This however is a matter of preference.
In this build, I prioritize Tumble over my other skills in most games. The reason for this is because the extra damage from it is large, it allows for dodging skill shots, and the ability to get that last little bit of distance for Silver Bolts is a large advantage. That's not to say that I go this route every game. There are games where the opposing champions are all, or mostly, tankier than normal (i.e. champions like Jax, Nasus, and Olaf). In these cases, I prioritize Silver Bolts with the same importance as Tumble to counter their larger than normal health pool. I always start the game with Condemn. Condemn is a MUCH better skill in Dominion than it ever was in Summoner's Rift. Almost every place on the map is within easy striking and pinning distance of a wall. This allows the utility portion of this skill to be much more viable and much more damaging also. Generally, I don't level Condemn up a whole lot because it's the utility, not the damage, that is the most useful part of this skill and since the stun doesn't increase with level, and it still does take a little bit of skill to pin, I would prefer to take a safer route and add damage to skills that I know I can hit every time.
To start, I get Prospector's Blade and Boots of Speed. The Prospector item gives me some early game health, attack damage, and a little bit of lifesteal. But it doesn't build into anything! I know. But the very first team fight (usually at the Windmill) happens less than 30 seconds after the champs are released, and you're going to want this little bit of extra umph to get you through (remember; shorter, faster paced game than Classic Summoner's Rift which means that items that give benefits sooner are better).
Next I get Berserker's Greaves. These give me a decent bit of cheap attack speed to proc Silver Bolts more often. Mercury's Treads are a good choice in games where you know that there's going to be a lot of CC. And if you don't feel fast enough, get Boots of Swiftness.
Kitae's Bloodrazor and Ionic Spark: Examine the other team for a second and ask these 2 question. 1) Is they're main damage dealer a brawler with a lot of HP like Olaf or Jax and 2) Do they have more than 3 characters that aren't 'squishy'. If the answer to either of these 2 questions is 'Yes', then get Kitae's Bloodrazor next. If not, then get Ionic Spark. After you got your 3rd item, work on the one that you didn't get. This will turn you into the DPS machine to fear.
Entropy: This is like the Frozen Mallet for Dominion, but it's better. Why? It has an active, and a really good one at that. It passively gives a 35% chance to slow, but upon activation, the chance is increased to 100% and your attacks start to do true damage. This is like procing Silver Bolts for flat damage every single time you attack. Want to turn the tables in a fight real fast? Activate Entropy.
Tip* I always put this item in the same slot every game. For instance, I always put it in my number 2 slot, so that no matter what, I know where it is.
My last item is situational. For ideas, read the next section.
Vayne is best in Dominion when she can take down enemies quickly. While this may not directly influence the rate that you get capture points, having a key member of the opposite team dead for a teamfight, or having them unable to cross the jungle to get at one of your own capture points is an extremely valuable weapon in a game where time is the biggest threat you have. Remember, you only have to be winning by 1.
A significant part to playing Vayne is knowing when to attack, and when to back off. She is an assassin, so definitely go into kill an enemy, but don't valiantly hold out against 3 or 4 of them. She doesn't have the durability to buy your team any real time to get to the defense and there's no way that she can hold off that many at once. In the end, you're better to your team alive. Learning when to engage will dramatically increase your score and ensure your importance to the team for the whole game.
The following is a little explanation as to how I use each individual skill in Dominion. Some of the techniques are similar to Summoner's Rift, some have a slight twist to them. You start the game with access to all 3 starting abilities, so knowing when and how to use them in tandem will increase your effectiveness and score while earning you a lot more kills.
Not much to say here. The 3rd hit is the most important, so make sure you get it. Tumble and Night Hunter will help you with that.
In team fights, hitting one enemy 3 times will do a significant amount of damage. But this leaves you with a dilemna. The close quarters fighting of Dominion is not like the spread out, mobile fighting of Summoner's Rift where the only real way to get a kill is to focus one enemy down while they're around. Dominion is much more team orientated, and so sometimes being a team player is more important than getting the kill. So how do I help? Getting 3 hits on an enemy, then switching targets to hit another 3 more times spreads out the damage, allowing some of the other champs around you with AOEs and and tanks with CC to mop up and win the teamfight.
But why change strategies? Well, let's say we don't and we go ahead and take down this one enemy. That leaves 3 or 4 more around you, and they're all just as fed as you. And let me tell you, they're not going to be focusing the tank. Switching the targets increases the chance that one or more enemy will back off, or it increases the chance that more than just that enemy will fall thanks to your team. ALWAYS COUNT ON YOUR TEAM FOR AT LEAST 2 KILLS.
This is one of the very first guides for Dominion, so there is bound to be some new strategy or some bit that will eventually come out or that someone will come up with. I'll try and keep and eye out for that and will be upgrading the guide accordingly.
Meanwhile, any comments or questions that you have are more than welcome. I just ask that any comments that you do make are explained and please don't downvote based on only one part of the guide and, if you do, please explain the reasoning behind it.
Mobafire is, in my opinion, not a competition to see who has the best guide, but a way to compare playstyles and guides to try and learn something. Not commenting on what you thought was wrong denys me and other players this chance.
That being said, thanks for reading this guide and good luck on the Crystal Scar!