sentries actually were fairly weak at certain point, like year or two ago. Then guess what happened? Well I don't know either, maybe some T7 of "devs" lost a fade on turrets or smth, and got angry and talky... either way, they nerfed sentry guns even further, increasing both tres cost and supply demand, and also making bile bomb bio2, so that sentry rush will inevitably met with bile on 2nd minute. Now almost no one uses them.

on the bright side, MACs costing only 3 tres helped, in fact they soon got nerfed to 15 supply so they can't be spammed - still nice to field one or two to make phasegate on your base or repair naturals

Really sucks because turrets were practically the only way to keep naturals safe for marines. Meanwhile, aliens get hydras and whips on pretty much every resource node. It's dumb.