You've got the play style down, but I heavily disagree with your item choices.

Meki Pendant - Bad first choice. You're very squishy early on and your innate will give you more than enough mana regeneration until the mid game.

Chalice of Harmony - This is a very good item on Swain, but only after the laning phase. As I said above, your innate will keep your mana up as long as you aren't spamming spells. Spirit Visage would be a much better choice here.

Rylai's Crystal Scepter - As much as I love this item, it's a terrible choice for Swain. HP means nothing without MR or armor, that 500 HP is trivial when you're getting focused. The AP bonus is pretty big, but will only amount to about 212 extra damage over 4 seconds, and given that you could get a Zhonya's Ring for roughly the same price, the AP bonus from Rylai's just isn't worth it on Swain. The slowing effect is the main selling point of Rylai's though, but you already have a slow, and with a rather short cooldown to boot. Nevermore snares the target, making the slow useless, and combining the slow with Ravenous Flock is completely useless since Ravenous Flock doesn't prioritize champions. Most of the time you'll be hitting the targets that you don't want to slow, and when you finally do slow the target you want, you could have just used Decrepify instead. Torment is the only reason Rylai's Crystal Scepter could be considered being a core item in a Swain build, but if your target got away from your Decrepify, what makes you think that you'll catch them with another slow? Randuin's Omen is a much better choice. It provides 90 armor and 300 HP, which is a much more significant amount of mitigation. The slow, while on a 60 second CD is reliable and can last for a very long time once you've built up your armor and MR. The only thing Randuin's lacks is AP, but this is made up for with 15% CDR, which will yield a very similar amount of bonus DPS.

Lich Bane - Simply put, not worth it. By the time you've acquired your 6th item, you'll only be dealing an extra 257 extra damage. Given the fact that you have a very low natural attack speed, you'd gain a much higher amount of DPS by getting something like a Zhonya's Ring. The magic resistance is useful, but not useful enough to warrant the 3470 gold that goes into buying a Lich Bane.

Frozen Heart - Good choice of item, but I still prefer Randuin's Omen in place of it. The golem buff will make the bonus mana useless, and the 9 extra armor isn't as good as 300 more HP. Randuin's Omen is also slightly cheaper than the Frozen Heart and incorporates an AoE slow instead of just an AoE attack speed reduction.

You have a sufficient amount of MR and Armor by the time you've acquired your 6th item, but your build is very expensive and the added damage from Lich Bane and Rylai's Crystal Scepter won't be doing much for your DPS. CDR is much more effective at increasing your DPS given your low ratios, and will allow you to snare much more often. Pretty good build nonetheless, but it could use some more thought put into how the items used will synergize with Swain's abilities.

I approve of this build. It was a blast playing. I went 32-6-10 in an 80 min game. IT WAS INTENSE!

This Swain build works really well, awesome job.

Good build but im just anti Frozen Heart but this is a support build so +1