HA-training a hive works supremely well, especially if the Aliens are on the offense. Yesterday while comming on TeamHoward, that exact thing happened : We held 1 hive and casually about ~6 RTs. We were doing fairly well ressource wise, had nothing except base and hive eleced, all the upgrades necessary were there (MT, PG, L3 Weapons, Armor1) but of course at this point the Alien team starts overrunning the Hive we have (10 minutes into the game approximately).
My team goes into its usual shouting of "OHMYGAWDCOMMUSUX BUILD TORRENTS NEXT TIME!", and this is where it gets funny. Not having built any expensive defense we had a whopping 180 res spare - enough to deck out the whole damn team in HAs, shottys and welders (7 player team, 6 in the field). We train out, run to Maintenance hive, setup a backup PG just in case and about 2 minutes later that hive is down. Another 5 minutes of blowing up almost everything on the map and aliens are down another 2 hives, from what seemed minutes before to be a simple win for them.
I'll still often siege for pubs, just because a) I have the res b] people on pubs can be so damn unreliable. 3 'rines out of 8 possible can hold down the siegebase, but they can't kill the hive by themselves. All in all though, siege really isn't awefully unfair - its usually easier for decent aliens to overrun a siegebase than a moving HA train.
But meh, basewrecking for Aliens when they're defended by 'rines is teh frustration ticket :/