Tips/Organizing for RPGs hosted via IM

I'm currently running a Dark Heresy campaign over Skype, with some help from Map Tools/ RP Tools at some point. I'm still learning that part.

However, my concern is that it's taking entirely too long. A single 2-hour session covered only one combat encounter with 1 (upgraded to 2) enemies, and even then I didn't bother with all the combat rules as I should've. If anyone has played it, I'm doing Tattered Fates: Book one of the Haarlock Legacy trilogy, and the players were only able to get out of the pit they start in, and did not even have a chance to examine the dead body because we were overtime.

Basically I'm looking for tips on how to speed up the game so that we can get more done in the same span of time and I don't end up running the campaign for a whole year.

Additionally, this thread can be used for organizing RP Gs over IM should anyone need it, to keep steam going for the thread.

I don't know how a single two-hour session covering a single combat is that different from face-to-face tabletop, but just to be sure, are you using text messaging or voice chat?

Text. And for comparison, I had preciously done a test scenario just to see how long it would take and to familiarize one of the players with the rules. 2 low level enemies and 1 slightly higher level enemy vs two P Cs. It lasted 4 hours.

Also for comparison, I play an IRL DND game, and we also had a combat that lasted 3 hours. It was with 5 P Cs against 7 enemies. That's a big discrepancy.