2.) We've seen baradium bombers spawn during a walker burn phase. This seems to happen most often during the 3rd (last) walker burn phase, after Kephess is already on the ground. We'll be DPS'ing the walker and suddenly another bomber spawns.
As mentioned earlier by another poster, a 4th bomber can spawn when you are burning down the walker if your group barely made the timer for killing the 3rd bomber and took some time to move to the walker to start the burn phase. This is due to the script thinking that you have failed to kill the 3rd bomber.
2 suggested ways to handle it when it occurs are to either have a tank taunt the 4th bomber and keep him occupied until he explodes on his own, or just have either a sage/sorc or merc/commando CC the bomber and let him blow himself up when his timer is up.
5.) Last but not least, we've seen the walker charge up his cannons for the saturation fire, our group moves out of the zone he's aiming at, and then he'll immediately turn his head and fire in another direction (usually on us). It was my understanding that he is supposed to do the saturation fire on whatever zone he is facing when charging his lasers.
There's a fixed pattern for saturation fire throughout the fight.
From where you face when you zone in, there are 5 sectors in the field where saturation fire can occur. Assuming a semi-circle area in front of the walker, the sectors are:
A - directly to the right of the walker
B - midway between the right and front of the walker
C - directly in front of the walker
D - midway between the front and left of the walker
E - directly to the left of the walker
For phase 1 and 2, i.e. imperial siege droids and trandoshan adds, the walker will fire in this manner:
A > B > C > D > E > D > C > B, and it repeats the pattern again.
During the period of time when the 2 pulsar droids are on the field, the walker will only alternate between firing at A or E.
Once the pulsar droids are killed and Kephess jumps down onto the field, the walker reverts to the first firing pattern, i.e. going from A to E then back to A again.