nyslater
If someone has an 80% heal reduction in a game, they can't be really be healed through damage.
Right, which is the entire point of this debuff. You can heal enough to prevent dying from a dot, but if a mob's on you, it needs to be mezed, stunned, rooted, or taunted off -- and fast.
in normal group play a good Shaman is going to have the 80% consuming pact healing debuff
up almost all the time except for very small windows.
Only for shamans who refuse to adapt.
Example best-practice for new usage: big pull arrives: shaman expends most of his bar healing while all mobs get aggro locked, mezed, slowed, etc. ONCE that stage is done, the shaman now cannies up, then meds/heals others while all the mobs are killed, assured that he's at no risk.
Killing those mobs should take 2 minutes, but if not, then either:
a) the puller ensures the next pull is easy, or
b) the group waits till the timer is nearly up, or
c) the group is prepared to adopt tactics that don't require the shaman to draw aggro.
You can't usually predict a bad pull 2 minutes in advance...
Yes, but any good group can nearly always predict the potential for a bad pull before it happens. And regardless, when you DO get a huge bad pull, the worst thing a shaman can usually do is lead off with the highest aggro spell he has (as he admitted he did).
you need to make the choice to stop hitting Consuming Pact 2 minutes ahead of time,
and that choice for flexibility will cost you quite a lot of mana....
Again: that's the entire point. You now must be judicious in using it -- you can't simply continually spam it without bad consequences.
Still, I repeat: two minutes does seem a bit extreme. Around a minute makes more sense ... or possibly start the debuff at 100%, but have it roll down to 0% in 90 secs time -- so, say 45s after your last cast, you can get healed for 50%.