Ah, I just saw it. I missed that only left and right slots count...From what I can tell by the diagram, there will be 2 in the middle row and 6 in the top and bottom rows that will be unadrenalinable.
15 / 23 is still pretty good though I guess.
As long as mass cc and shields can affect them (as is stated in the notes) it shouldn't be too OP. Plague, thornshield, and fire shield will eat them very quickly with adrenaline up. Flooding will be very useful too.
Lastly, as you noted, the edge ones will be vulnerable so a player can always chew their way in.
I would say they should be given a little lower hp though. The upped should maybe be lowered to 2. The unupped should probably be 3 as or 4 at most. This is because mass CC won't do more than 3 damage a shot at maximum (except pandemonium, but that is not guaranteed). This is the best way to keep it from getting OP with combos like the one above.