I have really not had that problem to be honest. I'm still a semi-noob on Heroics (SP, Crypts x2, UB, Bot, Mech <--as of last night)... but so far T.Clap gives me more than enough aggro to keep the mobs attention off the healer.
I think there's a bit more to this question... can we see your Armory link? My Dodge is like 17.58% currently, Parry is 16.5%? so I don't absolutely need the major heals off the bat. 13,333 armor.
So your gear might be an issue (not saying it is.. but it could be). The healer might be a healbombing healer. Love priests, with fade and that Proc heal (forget the name). Pallys are my 2nd favorite... they can take a bit of damage if needed.
Was your party CC'ing at all? How many mobs were you tanking in a HEROIC? Last night in Mech our only CC was a Mage. :/ We managed, but it got dicey at times, and we did wipe a few times on that last crappy hallway to the last boss. We did 1 shot the 2nd fire girl boss tho
Without good CC, you're taking much too much damage, causing the healer to drop dem heal bombs early, before T. claps can hold them.