You will want Peltasta in the mix for sure.
Maybe not necessarily C3, since that would make you good at tanking but rather bad at soloing, but you can’t really tank without Swashbuckling and an active block - which Peltasta has.
As for relying on Rodelero’s Slithering for magic immunity… I wouldn’t depend on it. It works (for now), but nowhere in the skill description it says it’s supposed to nullify all magic. Knowing IMC, this could very well be a bug they haven’t gotten to fixing YET.
Hoplite, on the other hand, seems like a more reliable choice. Finestra adds quite a bit of Block, helps with AoE (that +3 ratio is godly) and crit, and Stabbing attribute grants +25% M.Def.
If you do add Rodelero, you’ll be getting a good bit of CC, which is probably good for PvP.
Dragoon, Fencer and Doppel are DPS classes and add very little in the way of actual tanking, since Evasion tanking is not really feasible (too much unavoidable magic/missile damage later on).
But yeah, I do miss the good ol’ Reflect Shield…