I have pretty much every healer class covered as alts, in the 2 accounts I run, and the Defiler and Mystic are the most difficult to solo with. It's fine if you are going to be running with friends all the time in the game. But until you gain enuf AA to actually start doing some decent damage the Defiler and Mystic sort of blow compared to other classes in DPS and soloing.
Inquis rocks in the battle cleric mode, and is a fairly strong healer. Does good DPS too! The plate armor adds to survivability also. They solo well, and add some nice buffs to groups.
Templar is even better healer IMO, but man is painful as all get out to try to solo. Fantastic main tank healers endgame, for raiding. So keep that in mind.
Fury rocks, and is sort of like a Wizzy in leather. Does great DPS, but heals a little less I'd say than a Warden.
Wardens surprisingly to me are pretty much one of the best at everything it seems. I've seen some crazy DPS come out of Wardens that are specced right, and have good gear. I know of one Warden who can solo all but the final boss in the Eurodite Library, which is nuts.
It all comes down to what you enjoy playing. Each of these classes are important, and can be fun. Some have more limitations than others, but offer important buffs, and abilities to groups. Typically the classes that are the hardest to solo, you see the least of in end game. Makes sense don't it? The harder the class is to level, the less of the level 90 ones you see running around. And we all want to play a class that is wanted and needed don't we?
Have fun, enjoy the game. Make some alts, and see which class suits you best. Before long the class YOU want to play will become obvious.
Welcome to EQ2! I hope you enjoy yourself.