I recently had to transit at DME from Easyjet to Rusline on the way in then Izhavia to Easyjet on the way back. Both ways I gave myself 3 hours to transit in DME. I could have managed with far less both ways. Indeed I was favourably impressed by DME. It all worked very efficiently.
On the way in from LGW, there was no line at immigration and travelling with hand luggage only was straight out, within a few minutes. Checkin at Rusline was relatively easy to find, with an agent who either spoke no English or wasn't particularly friendly. I found the domestic gates at DME confusing as there seem to be two sets of gates with the same number but with a different prefix, which doesn't appear on the boarding pass. Getting through security was relatively painless and quick.
On the return flight with Izhavia, we arrived at a bus gate and my bag (wasn't accepted as carry-on) delivered within about 10 minutes. Had checked in online with Easyjet and did satisfy their carry-on rules, so went straight through immigration and security, again both quickly and painlessly.
Both ways I estimate from arrival gate to waiting in the departure gate area took no more than 30 minutes.