Trek to Madworld is kinda fun in a goofy, "We're doing a comedy episode now" kind of way, and David Gerrold's introduction is a classic piece of absurdism. But Death's Angel? I couldn't recommend that. I can't recall the mystery well enough to know if it was any good, because I was too distracted by the ludicrous aliens (giant blue crocodile...)
I find there's something quirky/worthwhile with each of the Bantam novels. Agreed that "The Galactic Whirlpool" is the most enjoyable (the sample chapters in "Starlog" made it the one I waited for with great anticipation, having only become an avid ST fan with ST:TMP, and my memories of TAS).
As a TMP alien fanatic, I should have liked "Death's Angel" but, like you, the coincidental analogies to Earth creatures was annoying. But a new friend I met not long after it came out saw it as a comedy and he thoroughly enjoyed it. Here he is, in a Si-s-s-s (click)
costume he created for a January 1982 ST convention:
by Therin of Andor
, on Flickr
The whodunnit aspect of DA was great; I didn't guess the antagonist and was surprised with whom the author chose.