SH bunker really isn't that hard to take (at least on my server where people are really heavily geared out). If alliance doesn't see you clearing it out, it can be done with 5-6 people easy, which is to say a warrior, any healer, and 3-4 of all the rogues/hunters out there. Defending it is also easy with aoe and hunters. Trap the bottom door, and as soon as people come in, use channeled aoe spells like blizzard and rain of fire and flamestrike, and nearly everyone's got a bunch of debuffs, DOTs and they're at like 75% health by the time they get to the flag to try capping it back. Only a zerg can stop it from being capped really. And destroying bunkers not only stops all the guards there from respawning, it also spawns some horde guards to replace them. Plus it's worth a lot of contribution points (that's the big reason to go after bunkers, but it does make capturing the subsequent GYs a lot easier).
Horde towers aren't as important as Alliance bunkers, because the big thing is, as long as our commander guy lives (not the big boss, but the guy who's basically the horde version of Balinda), they really can't progress since Horde defenses are all linear. I actually find that snowfall GY isn't that important, but if you can get it, you may as well just so the other team doesn't. But destroying SH bunker gives a lot of contribution points, it crushes that 2-pronged front of Alliance defense around the field of strife, and after that there's really nothing they can do to recover (ninjaing graveyards won't do much if anything). Balinda is kind of unimportant, but it's fun to send a group after her just to distract the Alliance.