Directing where towers shoot
One issue I've been having some difficulty with is where towers spend their time shooting. I'm noticing that the behavior seems to be that once a tower locks on to a runner, it sticks with that runner until it's either dead or passes out of range. That doesn't always seems optimal.
I see lots of cases where a group of runners approaches some slow down towers and some AOE towers (like the hive tower, for example). A runner will get tagged by the slow tower, slow down, then get bombed by the hive tower until it's either dead or out of range. Meanwhile, the larger group of runners (where the hive tower would have a greater impact) escapes untouched.
I've played other TD games where you can specify the rules for a tower (shoot at closest, weakest, closest to the end gate, farthest away, etc). I know if I were generalling these towers (which I am), the current behavior is not one I would choose.