It IS much stronger than playing assasin, as getting quick poison mean you get one TT piety every time you hit anything, and with dodge bought, and monotheism, you get as many potion boons as you have healing potions.
If you know your way around TT potions, 5 of each ends you with 10 improved cydsteps. And that allows you to walk through the goo floor in Gaan'Telet without taking a hit. Otherwise, It's not smart to sink your gold into poison that quickly as you can easily get it after killing some popcorn.
TT paladin is really really strong, and can probably beat Gaan'Telet with only Soul Orb, Patches, Knockback Mace, 50 gold prep and TT unlocked. However, I've never beaten Gaan'Telet (any version but the HARD one that ends the questline) without TT poison.