Honestly, Repair tool is probably fine, as long as none of the engineers have their cooldown; once that is in play, it can be oppressive, especially if multiple engineers are using theirs at different times on the tank.
Also, I think part of the problem is that everyone has 3 gadgets. In BF3 and BF4, not every engineer carried a repair torch (I know I often didn't because I usually carried a launcher and mines), but now in BF6, every engineer always has a repair torch (without even having to sacrifice for anti-tank), so there are just more of them in play constantly.
