I can’t really pick who I should use as my third slot. I am using Thor/Task but I don’t know who would be good as my third.
Any suggestion ?
PS: Sorry if this is the wrong place to ask.
Depends on what kind of playstyle you are going for. Are you trying to play a keep away (zoning) game, a rushdown, grapple, mix em up, etc.? Because whatever kind of play style you’re aiming for can help you narrow it down. I see Thor as a grappler type more than the zoning type, because his projectiles are slow, but his grapple and beatdown style does massive damage, and he has the highest health in the game currently, whereas Taskmaster is a fairly good rush, and is a really good combo guy with lots of unique tricks.
If you can explain your game plan a little better, then your choices become a little simpler. So what playstyle are you aiming for?
Well, I been messing around with thor a lot ever since mvc3 came out. I always thought he kinda was too slow, but I found out that rushing down with him is my best option with him, also, I enjoy rushing down someone. I can’t stand back at all, I need to get in there and do some damage.
I was thinking of using storm, but I don’t know anything about how people play her. When I do see people use her, I am discontent of using her.
I guess another good rush down character can do. I can already DHC Thor into Taskmaster 
Sounds like you could use some Wolvie. If you want characters who stay on top of your opponent Wolvie has pressure in so many forms it isn’t funny. Of course, If you have a team with nothing but rushdown, you may have trouble against certain teams if you don’t stack your assists well. You may need something to help with people who play keep away (zoning) strats. In that respect you may need at least one character who can break that long distance game to get in. Wesker is also a good choice, as his pressure game is strong when used correctly, and his teleports help him with tricky mixups and get in on those runaway players.
Other more experienced players may have different ideas, but those are some decent ones I’ve got. You could also try Dante, if you are willing to learn some muscle memory for his moves, or Magneto, Sentinel, or someone who has assists that can let you get in on your opponent, rushdowns and grapples are good damage, but zoners will give you problems unless you can pin them long enough to get in on them, so whoever you choose, make sure you use a good assist to them as well. Cover your weaknesses by using your assists to your advantage.
If you’re looking for a third character, Felicia might work. The only thing she CAN do is get right in your face, and she’s a great anchor because of how well she does in lvl 3 X-Factor without assists.
That said, she’s really hard to use, and somebody else might suit your team better, like West Daniel suggests. Magneto, Dante, Wolverine, and Wesker all seem like they would suit your tastes.
Hmmm, I gotta check out how well it works out. I most likely sticking to Wesker just because of OTG. Thanks a lot guys