I like the distance change so far, seems a bit harsh though. Might be good to test out 1.4 instead of 1.6. People should be encouraged to walk closer and not just wait on their towers to get LOS on someone, so the idea is good. Dropping it to 1.2 - 1.3 should be fine too if it's accompanied by some resistance buffs OR avg dmg nerfs. The HP penalty to dmg should increase a bit as well, every tank hitting 700-800 isn't healthy... On the other hand, to reach these values you need to put points into aiming, which puts your tanking abilities down a bit. So maybe it's fine?
Anyway, the elephant in the room is still Union set. Unless Inno is willing to make changes to that abomination (as mentioned before, nerfing sector dmg is a good start) dmg will still be reigning because tanks don't have the sets to compete with the additional 700 points that Union gives. It's getting buffed with this formula, so it's only appropriate to see some nerfs for it as well.