Either vast chunks of Robert Holmes's scripts were being hacked out (presumably most of the humorous scenes), or else Holmes was clearly flagging during the writing of this episode. The total duration for Episode Three is less than 22 minutes long, and the reprise from the previous episode's cliffhanger seems to go on forever.
It's not that this episode, or indeed the entire story, is bad. It's merely becoming the victim of bad circumstances. The model shots of the refinery suffer from being shot from above (and in real time as opposed to the usual slower speed used for such shots), but the water tank that was used for the model was inadequate. The camera operator on location, ill advised, completely masked off the top portion of the location footage to accommodate the model shots of Kroll to be inserted later. The result was a hard, dividing line between the live action shots and the model shot of the giant squid.
Having said that, though, the realization of Kroll, like the CSO in Underworld, is vastly overstated in how poor it is. The matte line does reduce the impact some of the shots used, but the monster is still impressive enough, and Kroll probably has the most realistically moving tentacles ever seen in Doctor Who before or since.
Rohm Dutt's death, though, and especially The Doctor and Romana's reaction to it, further hammer the point home that Time Lords are entirely different to humans when it comes down to it. Rohm Dutt is dragged off by Kroll, and The Doctor and Romana coldly analyze what just happened, and The Doctor even criticizes the gun runner for his foolish actions in getting killed. The scene reminded me of a similar one in Pyramids of Mars when The Doctor discovers that Lawrence Scarman is dead, but than callously brushes Scarman's corpse aside. Sarah is appalled at The Doctor's reaction then, but Romana is completely in agreement here.
This may seem like a minor event, but it serves to point out one of the great failings of the later Tom Baker era. But more on that later...