4 individual hunters and 4 individual mages will global people but when you box them, the moment melees start swarming you, you get killed because you can't IWT to face them so you have to keep moving around wasting time. This is the main reason I stopped playing any ranged/caster classes. One annoying rogue will make your life a nightmare.

The solution to beating hunters and mages is to roll 10 box like a boss. I do resto shaman, resto druid and 8 DKs. I'm still at lvl 85 with only 1/4 of Jade Forest done and I'm killing 2-3 lvl 90s at a time. I ran into mage, hunter, spriest ironically and killed them all.
My team will destroy at 90 in full honor gear.
But the secret is in having 2 healers not one.
And if it gets too tough I will swap a dps for another healer, but I doubt it will be necessary.