I've played a bunch of games with and against this playlist:

.9490 4 Briarberry Cohort
.4068 4 Thornwind Faeries
.3253 2 Rootwater Diver
.1687 4 Rootwater Hunter
.1274 4 Mawcor
.9259 4 Silvergill Douser
.14482 4 Reef Worm
.126 24 Island
.2280 2 False Demise
.11115 4 Diminish
.13357 4 Vial of Poison

The AI has cast Diminish at the most senseless times imaginable. Most of the time before combat on vanilla 1/1's and at the first opportunity it had. I'm not sure I've seen the AI more trigger-happy with anything but card draw and scry cards, if even that. Is there a way to make it not cast it on 1/1 creatures and not cast it unless something will die as a result? It's just not using the correct AI for it, take a look you'll see what I mean. It's a very rare effect currently it'd be really good if it was usable.

Also, the AI seems to be way too eager to chump-block suicidally with Thornwind Faeries. I've seen it attack suicidally with Silvergill Douser (as if it thought it can use the -X/-0 ability even if SD is tapped).