Would the hand tremors affect how accurately you can use your thumb? I'm asking because I find MMO mouses to very convenient, because the buttons are easy to reach and you can map exactly one action bar to the side buttons and then another action bar with the Shift modifier, a third bar with Ctrl and so on. Using one of these mouses you wouldn't have to move your left hand from the WASD keys and the right hand is still available to pan the camera and click objects while doing a rotation.

My own mouse is similar to this and I have no regrets.