Maybe you could try farming dungeons a bit below your level to get some gear before moving on. As your toons all use the same AC and it's quite a while before you get dedicated tank loot I imagine you'd need to do quite a few repeats of places anyway to get gear for everyone.

I've got one team without any BoA items and they are only now getting what I'd class as well geared (at level 35ish), it's a mixed class team so probably easier to gear and with 4 ranged probably easier to do runs with. You most likely won't be able to rep up your alts with your guild, my highest team is at 52 and they are still neutral (luckily they are the ones on the same server as my 85s), so I think transferring someone over will be the only way to get BoAs for leveling. If you can get geared through running lower level dungeons or purchasing a few cheap items off the AH then you might be able to get to the stage where you can do stuff at the appropriate level.

You might also be you need to play around with different ways of doing things (using stuns, kiting with hamstring, taunt rotations) to be able to get stuff dead. My second team had quite a bit of trouble on the last boss in SFK because I had no way to interrupt/remove the curse and was lacking aoe for the adds compared to my first team. I eventually managed with careful positioning and /target macros on the dps (also tried switching my tank and healer, but they didn't have the offspec gear to be viable) but there were a lot of wipes before I found a tactic that worked.