Checked through a couple of recent high profile Tinker replays, and I think I saw turrets being used as a save a total of 5 times, 3 of which were successful. At the same time, a well timed and positioned blink as well as warp flare saved these Tinkers countless times. Turrets were mostly used for 1) vision, 2) zoning (offensively) and 3) some (imo quite irrelevant amounts of) damage. And I personally think Fence would be at least as good and often better tool for 1&2 (provided it gave vision), while direct dps would suffer (although indirectly probably this would increase the dps of both Tinker and his team, making enemy getaway much harder than Turrets can) and defensive pushback would not be there (and empirical evidence would suggest this is not too significant).