They aren't, but then again they're abilities don't need them to be. They just adapt to most powers, and shut things down. I've seen some pretty powerful Mindless Ones in comics, but power in this case won't be enough.
Mindless Ones are highly inconsistent in their showings, so it's hard to say. I can't remember how easy it is to shield against their disintegrator beams, and not sure whether the Sentinels can adapt to that sort of magical energy. If the Sentinels can adapt the MOs are probably toast but otherwise they are going to be taking some serious damage.
If the armies simply open fire on each other at the outset, I can actually see the Mindless Ones having a good chance of winning because the Sentinels won't get time to adapt.
If the Sentinals cannot effect the magical properties of the Mindless Ones, (at their best showings), the MO's should win, a majority.
Unless there is evidence showing that, for some reason, Sentinals can counter a disintegration beam, shrug off class 100 berserkers, or easily wipe out MO's.
After all, Classic Mindless Ones were very durable and were never meant to be written as "fodder", which is what they have become.
The question then becomes: did the Sentinels ever adapt to magical attacks? Or just mutant powers?
__________________ Chicken Boo, what's the matter with you? You don't act like the other chickens do. You wear a disguise to look like human guys, but you're not a man you're a Chicken Boo.
Well, it's logical u would think that, since the Mindless Ones have existed in books for 33 years before u were even a blob of fertilized tissue capable of fitting in a petri dish.
But, for now i'm going to veer away from your extensive comic book experience and articulate delivery.