Viability of Swain? I find that he can viably play 2v1 bot if you're passive for the first few levels.
I find that if you want to easily survive bot 1v2 as a character like swain you need to play safe and maybe even alter your build a bit.
I know its strange but starting with dorans shield will do wonders on him, also so long as you CC anyone that tries to jump on you then you wont get pushed out of the lane as easily.
Swain is among the best mages for TT, despite having lower "Nuke" potential he has great survivability and great AOE damage.
Swain also happens to be among my favorite characters in the league.