Looking for group composition advice... currently have 3 hunters, shammy heals, pally tank.

Hi guys! I'm Althorius from Korialstrasz Horde, and I just discovered this website, it looks wonderful, and I'm glad to know I'm not the only one. I'm sure you guys are familiar with the random comments people come up and make, so far it's been about half 'omg dood u pwn' and 'REPORTED!' LOL. Anyway, hello to you all.

My current group composition is 3 hunters, shammy heals, and pally tank, and these are all 68-69, I plan on dinging 70 today. Then I will replace one hunter with my main, BT/Hyjal geared hunter. I have so far, without using my main, managed to solo ramparts, bf, sp, and ub, that's all I've tried to do, been more focused on just lvling than anything else. I'm pretty terrified of going into a heroic solo, I suspect I will experience a lot of wipeage.... My question is this: so far I have not even played my pally tank, I just have him assigned to buffs, crusader, and heals. The pets have been adequate tanks, on difficult bosses I lose one or 2, on Gruul I lost all 3 and had to dot him and back away, I lost 2 hunters but I managed to get him at 68. Anyway so far I seem to be managing OK without using the tank... I am wondering if perhaps I made a mistake using a tank. I've been thinking of eliminating him from the group and using 4 hunters, keeping the shammy around for pet chain heals, totems, and reincarnation. However I have watched numerous videos, mostly shammies (can't seem to find 5boxed hunter videos) of 5DPS classes doing just fine, so my question is: do I need a 5th hunter? Will I be able to survive those nasty heroic boss fights without a tank, being hunters only? Do I need to keep the shammy? Or should I be using the pally tank? I really don't know, any advice would be helpful. I'm thinking that with 5 hunters I'll kill bosses faster, but the offset will be I lose possibly all 5 pets each boss fight with no chain heals, the Mend Pet seems to have been nerfed since 3.0.2. And without those heals/resurrection, I could potentially be doing a lot of running. Please advise. :)