I "feel" like I do a lot more standing around in TOR as a healer than in WOW or Rift. The healer skills for a Sorc are fairly slim and rather straightforward. When to use quick heal is about the most demanding decision in an OP.
Playing the BH healer is slightly more involved but it's mostly a matter of CDs and heat management. Altogether, I would say BH healer spec is harder than Sorc but reasonable in difficulty.
By contrast I felt healing was far more involved and complex [decision hierarchy] in World of Warcraft as a Druid, Paladin and Priest. However, I only played those classes years ago during Burning Crusade. I suspect much may have changed since then as I do not play WoW currently.
Rift's healing roles were less complex than WoW's but more attentive in my experience. Forcing me to play more attention to my actual heal bar; CDs, rotation, targeting, debuffs than most modern MMOs.
I would say the pace of TOR is a lot more relaxed than either Rift or WoW. If we are to use two MMOs close in style to TOR.