Actually if you want to level you should be happy to get Praetorium.
CM is actually closer to 35 minutes. If you get even just 1 or both tanks that are new, that can increase to 45 minutes if they do not know the order to go in (*cough* like missing out on the incidiaries) and a lot of the other players just follow along without ever paying attention to that, so backtracking can easily add a lot of minutes to a run)
Praetorium is 45-55 minutes. So it's less than double the time of CM, while giving MORE than double the exp. A lot of people don't realize that the roulette exp reward actually DOES change based on which of the 2 dungeons you get.
So while Praet might take longer, it gives a better experience per time ratio.
And the reason I know that is because unlike a lot of other people, I did not go by "feels like".
I actually recorded time spent and experience given for real runs both before and after the patch in order to make my comparisons.
MSQ roulette likes to give me CM, and it annoys me because I know it's the inferior leveler AND it has at least 3 annoying CS right in the middle of battle. Praeorium's CS are at least in between battles so you can feel safe to step away.
CM however is dangerous to step away from during those CS. Since this game is horrible at applying things to a party at exactly the same time, some people's CS start 1-2 seconds later and thus end 1-2 seconds later. That means for a brief few seconds, someone becomes attackable while the rest of the party can't do anything. That means that the healers (which is what I usually queue has) have to IMMEDIATELY heal that person or they will die. Praetorium's CS never have that.