How can I clear up humanoid lags, without getting rid of the humanoids?

Hello there! I am currently creating a MOBA. And as many of you may know, MOBA's consist of many minions. Now you see, my problem is this: 6 minions spawn from each lane, on each side. Meaning its 6 * 2 (Both sides) * 3 (Number of lanes) And apparently because of the high number of Humanoids, the whole server starts to lag... And im not talking about FPS lag, im talking about things being slow and unresponsive. For example: My turrets missiles are moving WAY slower than they should (Using RocketPropulsion), and they move just fine when there are a little amount of mobs. Also the detection of enemies within the turrets range is slow and doesn't react like it should, however it works just fine when there are a little amount of mobs.

So basically what im asking is this : How can I reduce the server-side lags, without getting rid of all the humanoids? (I need those minions :<)