I played SWTOR quite a bit (Legendary, Living Legend, etc.), and beyond having at least one class to cover each basic archetype (Fighter, Mage, Healer, Rogue), the class scheme is not directly comparable.

Speaking as someone who played SWTOR from launch and really like the game, I have to say that WoW is better, especially with the recent change in direction that SWTOR has taken. WoW as it is today is especially nice for brand new players going through everything in the game fresh and who haven't seen and done it all ten times over already.

Shaman may be the only one that comes sort of close to Merc as a whole since it has healing, ranged damage, and melee damage specs (if I remember right one of the Merc DPS trees was supposed to be a "mid-range" spec, which basically means melee). But the way the class does those roles mechanically is not going to feel very familiar to you.

I would agree with the other recommendations here to just pick a WoW class that is well known for being new-player friendly and don't worry too much about trying to find something that feels like what you're used to. Just go with a class that will make playing WoW fun, and you're more likely to stick with it than if you try to find a class that will make changing games easy. You'll be re-learning everything anyway.

Hunters can't heal, but Marksman will feel more like Arsenal than anything else probably, if you just want straight ranged DPS that stands back and shoots stuff really hard. They also have the most developed pet system, which will feel closer to the companions in SWTOR than anything you'll get from other classes, and your pets will be able to tank and kill quite a bit on their own in the solo game.