That is a question that altaholics often find themselves faced with. It is also a question I often answer people that ask me that with another question. What do you like to play?
Never undervalue the concept of "what you like to play". I am a firm believer that you will also do better at something you enjoy doing, something you are comfortable with.
Your raid might need a warlock, you might have an 85 warlock, you might have all the knowledge that is out there about warlocks, you might have addons just for a warlock, you might have spent hours on the dummy on your warlock, but unless you actually like playing your warlock you will never reach your maximum potential.
I am sure you have run across the type on your server, in a LFD or even LFR, someone that does not really have great gear but seems to get every bit of potential out of it. A lot of that could very well have to do with what we call skill but I say it is because the person is comfortable with the class, they like playing it.
A good example of what you like to play would be three mages on my server that I know.
Mage A - Loves the class, can tell you the tool tips verbatim, he knows all the lore about mages, if you ask him his rotation he will spit out the standard and then just add that there is so much more but if you ask him to go into it then you best be ready for a three hour run down on all the little details about when to do what and why. He knows all his stats and what he should stack but unlike most he can actually explain why those stats should be stacked. All of this, without any effort. He just loves it so learning it never seemed like work.
Mage B - Might not know the tool tips verbatim like A does but know his whole toolkit. He will know the stat weights and rotation but only because it is what he read, not because he really cares. He will get a lot out of the class, he is the standard "good mage" you see. He works hard at doing as well as he does, but it is work for him. While he might enjoy playing the class he works to play it.
Mage C - Read everything, understands it too. He does not take as much time working on the little details, he does not worry about the tiny changes he can make, he can not adjust on the fly to the various different events that might pop up because he just knows to do what he has been told to do. He is a serviceable player and most might even call him good but when you look at the numbers you will see the difference.
I've run with Mage A, Mage B and Mage C in the last week.
They all have equal skills to follow mechanics, their gear is all within 6 item points of each other.
On the same fight with roughly the same buffs their DPS was as follows.
Mage A - 46K, Mage B - 28K, Mage C - 15K
That is the difference between loving what you do and knowing what you do.
The key is to be honest with yourself.
Someone might say now that they like playing their Rogue. Sure you do, you are trying to get a legendary but you don't really like playing it. You are playing it because you want to play it which is good, you are playing it because you have a goal in mind, which is good, but you are not playing it to its full potential because you are not really comfortable with it.
Playing what you like to play will usually always offer better results. You will do better doing something that you enjoy doing. Even if you are not well versed in the class, if you really enjoy it, you will do better at it.
Again, be honest with yourself.
And remember, just because you like playing the class does not mean it is right for you. You have to like playing it sure but sometimes it just does not fit you. Try something else, you might be surprised that you like that more.
I don't like playing melee and it shows. Sure, I can put up some respectable numbers on my enhancement shaman with all her ungemmed and unencahted gear that I have just for questing. I can throw up 20K in that junk with no problem but I do not really feel comfortable doing it. It feels like work and not like a flow. I can do up to 15K on certain bosses on my rogue and I am not even zul ready yet and while some might call that good, it is stressful and not enjoyable for me to do because I am not a fan of energy as a resource.
If I where comfortable I would do better at both. If I liked playing them I would move more fluid, I would think one or two steps ahead, I would actually be good at them. Do I like playing them? Sometimes, but not really. It shows to someone that is looking.
I've seen hunters playing and I can break down everything they are doing, as a hunter myself, and I can see who is really comfortable with their class and who isn't. They might both say they love playing a hunter but I can tell you just by looking at them that one is lying, to themselves.
All you really need to tell how comfortable someone is as a hunter is for them to move a little while fighting. If they can aspect dance while not skipping a beat in their rotation and not even stutter stepping while doing it, that is a sign of a comfortable hunter.
There are many hunters out there that can't do that. Most can't, but they are really good players.
Every time I see someone like that I think to myself how much better they would be doing something else. They might say, I love playing a hunter, but they are lying to themselves. Their actions tell me otherwise. They can say they love playing it all they want but their actions show that they are not really comfortable with doing it.
As a guild mate said last week, "I noticed that if someone is really skilled at one class they can usually learn a new one pretty quick and become good at it.".
That is so true. There is no replacement for skill and every class and role needs it. A skilled player can adapt to play any class and role as needed if they had to.
The difference is that a skilled player can play every class well, maybe even amazingly well, but someone that loves that class that also has skill will be exceptional. They will be something special.
The next time you see a really skilled player and they just seem as if they are really not that fluid in what they are doing think for a moment, they might be a really good priest but they would probably be a god as a warrior. Who knows without trying?
What Should I Play?
Everything. Test them all out.
Saying you love the class you play and it is the best class is all fine and dandy, class pride and all, but you can not really know if you love that class if you have nothing to compare it too.
One thing to remember is that it is possible to fall out of love with a class just as easily as you fell in love with it. If somewhere along the line you suddenly feel as if you are losing a step on a class you love and have played forever maybe it is a sign the honeymoon is over. There is nothing wrong with looking for something else to fall in love with.
Play what you like to play but be true to yourself.
You will always be better playing what you are comfortable playing.