You won't be soloing/moloing all RoS progression quests with any of them. You'd be lucky to Duo some of the quests. And the missions? I can't box RoS missions with 3 Mages, So, yeah. This expansion is a whole other beast.
The most powerful molo is definitely mage or necro. Aside from missions they rarely ask for help on anything or join groups to help others. I don't know about beasts, It's been a long time since I have seen one out by him/herself. The third class would probably be SK, they are all around pretty capable, but you would need to put a lot more work into them than a mage or necro.
I always laugh when I see people saying that magicians are the best molo class in game. Because while a magician can hold its own against one mob, I would love to see said magician break a room with six mobs packed into it. Or five. Or four. Or even three. Some might be able to handle three with requisite skill and talent and gear, but majority probably cannot. And how many times during progression have you only killed one mob with no adds? Just some things to consider...
As a main rading bst I can say we're not the BEST dps, but when it comes to solo/molo I can do this in RoS with no issues. Other than cats and cactuses in OT I can SOLO singles in any zone with pet tanking. Moloing I can handle two. Names are a different story I've only moloed two, which we're the Aug dropper in ST ( forget name, xalgoz or something), and the fereth named at the forge in Goro, so yah bst may not be the highest dpw but by God we can solo/molo almost anything.
think OP was asking about solo/molo thru progression not only static kills .. could be wrong.. but I dont think any class can solo/molo thru progression I would think you would need to at least 2 box .. some of those tasks/missions are difficult or complex for just 1 toon+merc at least from TDS on up maybe TBM if your 110 and RoS geared
Best class is the one you know. Todays eq we are all equally as good and equally as bad. All the casters classes can do great dps and minus the wiz, molo decently enough to accomplish most stuff. Your pure melee will need some help but a monk, rouge, zerker and warrior can bust burn a mob or two then med (gear depending). The rest of the classes are good enough to do things but still need help.
I'm curious which class you would consider better, I know mages arent invincible but you have to admit when you reduce it to solo/merc they are up there.