Least taxing class on my hands

[chief pokishi]

Cleric is perhaps best class for you. Having leveled up to 45, I'll tell you all you do is sit and heal when needed. Sure you can throw a root or DD occasionally but you just heal. You can set up macros to handle all your buffing too.
Wizard is another click and sit class. My only issue with say a Mage is when you need to control your pet in a sticky situation. You have to spam "pet back" quite a bit to get off say a rooted mob or not to attack a mezzed one.
I suppose though you should perhaps just try out a class and see how taxing it can be to your hands. Though honestly, I wonder if the clicking won't be to bad but the typing in group chat. Then again, macros can take care of like 70% of the convo.
Good luck in choosing and welcome to the game. Hopefully your arthritis won't be too problematic. This really is a fun game.