
Just looking at the numbers--1 resource for 2 Health & 2 Sanity--Dr. William T. Maleson has the best cost-to-stat ratio of any ally currently in the game (as of The Path to Carcosa). Though he is unlikely to unseat his tenured colleague Dr. Milan Christopher, he is still a good choice as a second ally with Charisma; as a cheap, effective damage/horror sponge; as a target for effects that discard assets; or for investigators for whom Dr. Christopher's resource generation is not crucial.
Once per turn, his effect lets you cancel an encounter card at the cost of 1 clue. The good news: His effect is a reaction, so it doesn't cost you an action; being reactive, you can decide whether to use his effect after you've drawn the encounter card; it cancels that troublesome encounter card; and the clue paid to do so is placed on your location, so it can be picked up again with Roland Banks' effect, etc. The not-so-good news: This effect only works for encounter cards you--not other investigators--draw; the canceled encounter card is shuffled back into the encounter deck, not discarded; and a new encounter card still has to be faced. So, basically, unless you're using some sort of scrying, you've chosen what lurks behind curtain #2 to buy a reprieve against what's revealed behind curtain #1.
Is this effect worth it? That largely depends on how bad the avoided encounter was (compared to the new one drawn) and whether you needed that clue (and, if so, how effectively & quickly you can re-discover it). Maybe that was your only clue, so your Survivor investigator can use Newspaper to easily scoop it back up. Or, perhaps your Seeker investigator is keeping extra clues on himself/herself for "I've got a plan!" or Rex's Search for the Truth, so can drop one without slowing the pace of the game. In any case, you're likely to use Dr. Maleson's effect on an "as-needed" basis rather than every turn, as opposed to other allies whose effect you might use each turn.
There's another use for Dr. Maleson's effect, though. Being able to put a clue back on a location with no clues can benefit several cards, including Roland Banks, Roland's .38 Special, Cover Up, Inquiring Mind, Preposterous Sketches, etc. Dropping a clue on a location in order to get that extra +2 from Roland's .38 Special or to use the 3 icons from Inquiring Mind can make the difference between success & failure. And, since Roland's Core signature weakness, Cover Up, only works on clues as they are discovered, dropping one and re-discovering it in order to remove a clue from Cover Up can potentially save Roland some mental trauma. [I've actually encountered all three of the above situations when playing Roland.] [EDIT: A couple upcoming cards--Forewarned & Mysteries Remain (a spoiled alternate signature card for Roland)--also enable you to drop a clue at your location, perhaps indicating that more cards may use this mechanic.]
From the above, you can probably tell that I think Dr. William T. Maleson is a good fit for Roland Banks, for both his effect and as a cheap horror sponge. His effect may not edge out the first-choice Beat Cop or Art Student for Roland, or Dr. Milan Christopher for Seekers, but his super-low cost & good stats alone make Dr. William T. Maleson a good fit for any investigator that has a deck slot for him.
Here's hoping FFG releases an experienced version (or two) of Dr. Maleson (Working on Something Even Bigger/Truly Huge), perhaps with his effect upgraded to discard rather than shuffle the canceled encounter card and/or to allow his effect to target any investigator at his location.