Just my personal views....to be honest I didn't even know that the widows had shot blocking on their shots. Or I forgot ... or something. The only problem I've had with the widows in the past is that for such an agile enemy, they were also pretty tanky, so were a bit annoying to grind down. HP values might have changed recently, though, I'm not sure. I don't recall being annoyed by them lately, though.
Blademorphs since the nerf and move to Fearsome have become pretty easy, I think. I don't think I've taken a single bit of damage from those guys since. Regarding slow firing weapons, all you have to do is stand at mid range and the Blademorph defenses open up a fair bit. Even at long range I think a slow firing weapon can get through the defense with careful aiming. So, yeah, I definitely don't think there are any problems with those.
Edit: You could remove the widows shot_destroys_other_shots and change that to shots_can_withstand_x_shot_interceptions instead. This would at least allow more shotgunny or bursty weapons to push through the widow's shot.