Granted I don't play Dust2 as much any more with other commitments, but a few years back we actually ended up extending the round time because players at the time were not happy with the idea of being almost forced into rushes every round. And, to be honest, it seems like rushes will end up in a CT victory 9 times out of 10 anyway with how the map is designed combined with the number of players. Considering Dust2 is predominantly a server filled by non eGO members, changes like this should probably be avoided until we get those players involved in the decision.
For example, a few years ago when the server slots were expanded from 48 to 64, a large portion of the players were upset about this changed, partly due to the fact they had no idea it was coming. This lead to a bit of mayhem and several forum threads popping up addressing this. A common concern of the players was the amount of flashbangs, m249s, and of course the round time not being long enough to compensate for the new player limit. The solution? I spent about 2 hours a day for 4 days talking to as many people in the server as I could to get their feedback on the state of the server and the changes they would like to see. And, in the end, everything seemed to turn out great and many even contacted me afterwards saying they were pleased with the changes that went through.
So does the round time still need to be 3 minutes long? No, perhaps not. Maybe 2:30 is a slightly better round time. As I mentioned, dust2 is a rather unique server due to the large percentage of players that are not in eGO. If you'd like, I wouldn't mind helping you run this idea by the players of the server to see if we can get their thoughts and come to a nice compromise.