My new, more complete strategy for rigging a biolab ahead of a zerg.
Switch to engineer with tank mines. Go down to the vehicle spawn and pull a flash with 100m radar.
Rush to the space under each of the jump pads up to the launch pads and plant a
single AT where Sunderers usually park.
Now go back to the vehicle spawn room and switch out for any loadout with 2x C4 (I use my HA). Place one stick of C4 on top of each of your AT mines. Note that a level 3 (IIRC) utility pouch (200/400/500) with level 2 each C4 (200/500) and AT mines (100/200) will let you plant 4 of these AT+C4 mines, each able to destroy any vehicle without mineguard. Alternatively use it with AP mines to wipe out MAXes and flack armour infantry.
Now go back and leave your flash directly under the centre of the biolab. This will give you vision of anyone inside. It will need touching once every five minutes to keep from despawning, and will likely be blown up if they take down the interior generator, but it's worth it.
Switch out for and place all the AP mines you have around the shield generator, then switch to your favourite combat class and try to defend the outposts. If the fight comes indoors try to keep replacing mines as and when makes sense.
The name of the game is delaying them till your side can throw people at the problem. The mines plus radar make for excellent force multipliers, letting a small squad put up a good fight even when outnumbered, while the AT mines should help prevent them getting fast, close-in spawns. This is also a very good way to break zergs, as it denies them their vehicle advantage. I love it when there are a dozen tanks swarming around the outside of the biolab unable to do a damned thing about their infantry being locked inside a teleporter room.
And the great thing is you get bonus infantry resources from gaining experience in biolabs, so the heavy resource investment usually pays off by dragging the fight out, rather than just scrambling to grab some kills before you get overrun and camped.
EDIT:
Undocumented changes post. So far one important point;
Healing an ally damaged by friendly fire will no longer grant XP
I just wanted to clarify on this. It was a pretty nasty bug before. It's a bit convoluted so hopefully I can explain it. If you were playing as a medic, got team killed, then revived, it would save the teamkiller as your last killer. Now when you tried reviving people, it looked at your last killer, not your patient's last killer. Thinking it was a teamkill, the xp system wouldn't give you revive xp. This caused some medics to think they were locked-out. This should fix all that.
Also, if a guy is killed 100% team damage, reviving and healing them up to full won't grant any xp. Before you wouldn't get revive xp, but you would get heal xp healing him back up to full. That's more what the patch note was about. They left out what I thought was the more important part of the same bug fix.
Apparently the mini-chaingun changes (or at least the wind-up time change) didn't make it into the game despite being in the notes.
There are also some nasty bugs being reported, with some bases being uncappable and at least one spawn
dumping you into an infinite suicide/friendly fire pit of hell.Also reports of a huge increase in population XP bonuses, with people having 50+% bonuses when their faction has low population.