As soon as the staff can figure out the Issue that is causing the mobs to use A LOT of resources. When mobs are enabled there is performance issues. Hopefully in the next version of DW20 it is fixed. But be patient the staff are working hard on resolving all issues.
The dw20 server has not been updated yet. I just want to point out to @Slind14 that each and everytime I check the tps now on dw20 in the 24h no-spawn trial, I get 20/20 tps, be it 4 players online or 32. I've been checking for a few hours now, and it stays consistent.