Armor/Damage types, right?
Most powerful humans are heavy, which gets owned to stuff like chims, archers, etc, and most undead stuff is scrawny & weak (or massive & vulnerable to windriders/headhunters), and gets owned to a raider/grunt (or whatever) combo.
Orc burrows die faster than just about every other building anyone can ever build. The reason is 'cause of the armour type - it's not fortified, so it takes ALOT more damage from everything, except siege (of which I think it takes less.)
Solution: Reinforced defences.
When someone calls you a noob, reply thusly:
Everyone was a noob at one point, but only an idiot would think it a bad thing.
If you ever play Hu in 4v4 and manage to get gryphons while they have an orc without reinforced defences, you are going to have a fun time. There's nothing more satisfying than food blocking someone to 80/0 and killing ten burrows. If they're not nearby, it will often force a TP in vain that will always put you ahead, even if you yourself have to trade TPs.
This post is overwhelming conclusive evidence that gryphons need to be nerfed.