It's a good idea to make a card like spore crawler against ground units. But I think Sentry Gun is somewhat OP, and I'm not alone saying that.
Due to this long range and fast attack, this structure crushs too many units, even the heroes. Like spore crawler.
(10 warpigs with medic don't stand against 2 HP-boosted sentry guns). That make some decks (defense based) even more annoying.

Considering Mohandar is often in spore crawler range, I see more and more games ending with tanks or overboosted jacksons.

I agree somewhat but its a difficult topic, hard to balance this stuff. But I feel that now that protoss got another strong air-ship they are so strong with air attacks people feel the need to play defense/zerg against protoss. I know i do :P and it makes the toss weep tears shaped like little pylons.

why cant towers just be weak targetable and permenant. Would work a lot better than how it is now. I hate that you can invest 300 vespene into an attack just to be countered by some cheap *** defence towers.

clord just TRY towers like this even if you revert the patch after plzzzzzzzzz.

permanent towers could also turn to some insane stuff. defense decks could gather large amount real fast and become even more anoying than they are now.
Also if permanent towers were made weaker they would suck. that would be like using ghost that can't move.

Maybe you could invent new unit ability for them: unboostable.
that could be exelent solution to the problem :)

Today i saw like 10 void ray with shields go down from 1 spore

I just noticed that Emperor's Will works on defense structures (turret, sentry, spore). Needs balance there.

Emperor works on the turrets you start with in overmind, made it alot easier.