As a healer I find a lack of mouseover macros/support pretty horrible. I've played a healer in WoW for about 5 years now and while I love the healing style in ToR at the moment I think the interface could use a bit of love. It just feels quite clunky having to put my mouse over the player, click the player I want to heal while losing my current target, then cast the heal - with mouseover macros you can target whoever you want but the heal goes on the person your mouse is hovering OVER as opposed to targeting. Its only really a small difference but it saves a mouseclick and feels a lot smoother.
Target of target and secondary target would be really really nice. as it is, this focus target thing you can turn on in preferences doesn't seem to work at all, or I am just not figuring out how to use it properly. In fact its more of a hindrance than anything as it just forces me to click more often to select the target I actually want.