You're really pushing it with i76 and no +1 (in my honest opinion). It's not impossible, but makes life just a tiny bit harder, as for tanks I believe 5.7k HP should be minimum, the one that's very demanding is actually the DPS. Healers can get by as long as people don't die, thus exhausting their MP. With lower DPS you: Risk getting another WotL during heart phase, risk not killing adds in time before double plume, risk not destroying superbomb in time especially if a dps died (which they shouldn't, but let's face it, we are all humans and we lose concentration sometimes)

As for hard enrage, if the entire team goes with iLevel 76 I believe there might be a fair chance of getting him enraged (wipe earthquake I hear,never got there :P)

I'm like you, I don't really like going +1 so I guess at least you could try until you get more myth pieces.