Spawn times inconsistent

So when playing with unrelenting force it has a 3 sec timer before you lose the 1% per attack add to dmg stacks. Im having issues with the waves starting at inconsistent times. I try to time the estimated death of the last mob with starting the next level because i dont want to overwhelm my carry but some times the next wave is instant to spawn and others its 4+ secs after which then renders the item less usefyl as t has to start stacking back up. I noticed the auto start next level being too slow so i have taken it upon myself to start the next level every time manually when attempting to use this item. But every game, EVERY game the spawn times are so inconsistent that i can only get up to maybe 800 stacks before i lose them because i start the next wave, the last mob dies but then the next wave doesnt spawn for more than the 3 secs after the last mob dies. I have tried to suplement this with the dungeon door and holograms but they do not help when they get killed so fast that the creeps just dont spawn in time to keep the stacks. Can the next level button just auto spawn the next wave instead of having a delay please.

It seems to work quite nicely for me. If you want to maintain unrelenting force stacks, then make sure you use a carry that can reach the beginning of the map, probably a hitman or shadow. Although.... I haven't been using unrelenting force for damage, so I haven't paid attention to exact timings. You might be on to something here.

Yea I think if the time limit is increased to 4 or maybe 5 secs it would work without a hitch.