The turret is supposed to be a tie breaker, not a death trap. Its shots would definitely help you if you are 1v1 in an equal, even slightly disadvantage situation. But if the enemy gets massively ahead, a single turret should not be a anymore helpful. (it is still an additional 1000~ damage in a team fight regardless).
The correct way to utilize a turret defense is to shove the wave before it reaches the turret, then stay far back so the enemy couldn't dive.
A one point turrets were really op, but the game became so long and boring cause people never really get punished for their mistakes, so they got reverted. (If you are curious, at one point 2nd turret gives AOE recharging shield, the inhibitor turret shoots lasers that slows enemy, reduces their damage by 10% and shreds their armor. Ridiculous..)