That would make sense if the guards were only near the bridge closest to ally base, but those guards are at every bridge leading to the alliance "part" of TB. I actually don't get why they are there in the first place; TB is a pvp area, they are unnecessary.
Those guards aren't much of an issue when taken alone, since they got low hp and can be 1-2 shot. However, when there are players around that slow/stun/cc you, those guards become a pain hitting 25k on plate.
If you had to bring in the matter about the base proximity to the bridge, then you should at least add horde guards to the 1st and 2nd bridge, since alliance got guards on the 1st, 2nd, and 3rd one (with the 2nd and 3rd bridge guards being obviously farther from ally base than it is for 1st bridge guards from horde).