If both main forces arrive in the Biolab at the same time, the previous tactic won’t work anymore. The most important part in this case, is to regroup with all squads in the Biolab teleproter room ASAP (every second counts) and to destroy the SCU. For this kind of attack, you need “special” squad composition, which I call “assault squads”. They consist of ~ 4 Maxes, ~ 2 Engies and ~ 6 Medics. Maybe people will argue, that such squads don’t have enough firepower or it is simply a bad compostion, but my experiences in the past showed me, that with the right lead and teamplay, it is just perfect. Normally the defenders don’t have enough time, to regroup at the teleporter room to camp the attackers, which can take every point the leader wants, after they have regrouped. You should always send half your forces to the generator room and the other half to the small building next to the SCU. Holding this little building, will decide whether or not you will win the fight. As you can see in the picture, the forces in the building will prevent the defenders to camp the main door of the generator room or to flank the attackers from behind. The attackers in the generator room, should stay away from the doors, because of dropping C4 and rockets punishing in all the time and take care of the second level of the building, where normally a Cap-point is placed.
After the generator went down, the forces in the gen-room will breach out asap to the SCU, which shouldn’t be heavily defended, because the forces in the building next to it prevented it. Ones arrived at the SCU, the attackers will get a new defense line online with maxes ahead and support behind them. The most important tool now, are the revive grenades from the medics, which will provide a constant “revive field” at the SCU and in the small building, which are both under heavy attack. Ones the attackers successfully destroyed the SCU, they should still hold their positions and not breach out for the next ~20-30 seconds, because the remaining defenders still pose a significant threat and could clean the SCU area and finally repair it (yeah, I saw that in the past). After a short period of time, you will see a sharp drop of the defender population (even with a sundie on the ground) and you can leave your positions and clean the area.