I feel singed is one of the best tanks in the game. Mid-Late game if they focus you they basically have to blow everything they have to kill you. If you don't get focus'd you make them pay by slowly ticking their health down. If anyone makes a mistep thats when you toss them back into your team and they should get blown up. With this build I've found that you can be extra aggressive mid-late game and force the other team to make misteps.

I don't have all the runes I need/want yet so the set I have in this guide is what I use in game right now. I may come back and change it, but for now this is what I'm using. I like the magic pen because it does enough to help your poison trail without having to spend gold on it in the game. I use dodge for survivability. And I also use the magic resist for survivability.

I get the magic pen in the offense tree and then I just stack defense for survivability.

I start out with a Maki Pendant and 2 health pots. I turn that into a chalice which gives me enough mana regen for the game and it gives me a bit of magic resist. Then I get boots of speed. After that I go for Leviathon. After that I turn the boots of speed into the boots of quickness. After that I work on Rylai's. After Rylai's I get wardens mail and heart of gold that I turn into a Randuin's Omen. If the game is still going after all that I finish up with a Warmogs.

I like using cleanse and sprint. Between those two spells and your ult and poison trail you should be able to escape almost any gank.

Pros:
-Extremely tough to kill.
-Poison cloud punishes people that chase.
-Toss ability kills people who overstep
Cons:
-The only cons I've seen is that you can't push towers that good.

Early game you need to make sure you spray the creeps with your poison to make sure you get gold. Save your ult to win close fights. This ups your attack and increases your health regen. Mid-Late game after you get rylai's you need to make sure the other team is running into it during team fights. Usually you can go where you please except under an enemy tower. So weaving in and out of the enemies will make you the most effective. If any enemy oversteps you must be ready to toss them back into your team with your poison on. This will put them in a bad position and have to run through your poison cloud and take more dmg and they will be slowed. This is my first guide I've made so I'm interested in hearing some feedback.
Thanks
-Donkaynuts