I dabbled a bit over the weekend. While I still generally enjoy the combat, I think what I find tough in revisiting any MMO is that my upper level characters (I have 43, 58 and 72 characters, and used a couple of "off line" leveling points on them) feel like total strangers to me. I hardly know how to play them, what combos to hit, where to go finding new quests. I can certainly look all that up, but it's hard for me to just jump back in and play competently after so much time away.
The control scheme is demanding, especially when trying to jump back into a higher level character. When the first expansion came out I did exactly what you mentioned, leveling up a new character to relearn everything. Once I got my new character up to the same level as my existing characters, I felt comfortable jumping back into my existing level 60s.
The good news is that leveling is so much faster now. I got my new character and one of my older characters up to max level much faster than I expected (with help from offline leveling). It's almost too fast now because I was constantly outleveling content.