Did anyone have Urlgryber flee and rally with Eliza and Rayland? If so, did you abandon the ruse (that Eliza had planned) in favor of immediately assaulting the PCs, or did you come up with another tactic?
I was going to have him bolt as soon as it was clear he was out-gunned, but he never made it. If he had made it, I think its important for the story to try some form of ruse. Presumably, Ochymua is listening in through Arkley and will want to prolong the encounter in order to learn what it can by studying the PCs. If Urlg makes it up there, it will just make the ruse harder to sell. Perhaps Urlg could pretend to hold Eliza and Rayland at spear(glaive) point and try to get the PCs to back-off - or he might pretend to take the two as hostages and leave the tower. If Urlg gets up there and you just immediately have the trio attack the PCs, then you miss out on all of the oddness of this encounter and for the chance that the PCs can figure out that there is a sinister force behind the scenes.
Even if Urlg doesnt make it to the third floor, the players are going to see through the ruse because Eliza and Rayland have all of their equipment, something that wouldn't happen if they were truly prisoners. Also, if the players have done their homework on alpha-colony, that will know that Rayland should be the one calling the shots as governor, not Eliza. And, if they found the plum tree note, they should know that there was a schism in the colony with Eliza and Rayland on opposite sides. All of this, together with the slime, should cause more than enough suspicion to keep the ruse from succeeding for long.
I was really pleased how this encounter went down with my first group to get through it. The players had kept meticulous notes and accurately deduced what was going on - to the point of figuring out that Rayland was resisting some form of mind control and that Eliza was not (successful sense motives). Eliza perished in this encounter, but they captured Arkley and we even had a tense several moments as one of the players began roleplaying a one-way conversation/intimidation through Arkely and directed at whatever was controlling him. It took the rest of the players a minute, or so, to figure out what was going on and when they did there was silence around the table before one of them said, "Well, you've just guaranteed that whenever we meet the final boss, he's going to be really, really pissed at us."