Along the way our healer started asking to be guarded - a request I generally don't pay attention to. In hard modes I prefer to keep aggro on myself and with only a 66 hilt I therefore guard the hardest hitting DPS.
Actually in those new L55 FP's if you don't guard the healer and don't CC in general something tends to go for the healer. Healer aggro is much higher then it used to be and if the healer doesn't use his/her aggro dump it becomes really tricky with larger groups. Not that it's not doable, but I found that actually it makes sense to guard healers at times.