Linked below are some threads to help you do your research. (Some of them are quite old, so be careful with the conclusions).
You will be able to do normal mode instances all the way to L80 with no problem. Heroics are out of the question unless you outgear the content significantly, which leads to a chicken/egg problem of how you're going to outgear the content without being able to run heroics (answer is likely BG honor rewards, but this team is not a super BG team).
I'm going to throw out some links, but AT THE CURRENT TIME, I would not recommend this group composition. If you absolutely must bash your head against the wall, I'd recommend a druid healer. Wild Growth is nice for your swarm of pet-tanks, and HoTs plus healing buffs on the pet mean a continual stream of big heals which helps mitigate the low health pool and low tank-ability of the pets. Normal mode stuff will be quite fun and is very doable in WotLK content.
This comp was one of the most fun comps I've run to level up in instances. I shelved them within a month of getting them all to 80, however. It's not a great PvP team and it's nearly impossible to PvE with them.
If you're dead set on running some hunters, I'd recommend a Tank+Healer+3xHunter setup.
http://www.dual-boxing.com/showthread.php?t=27749
http://www.dual-boxing.com/showthread.php?t=16329
There's a good reason why most of the Healer+4xHunter threads died off 1.5-2 years ago. Be forewarned,
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