Wow.. two nice teams!
I tried playing around with Rexxar a few weeks back, but the double boomstick with rogues really can be what makes him a lot more playable. The problem is indeed, getting that first counter to make his attacks epic worthy. After that, the Boomstick with Misha being able to come to his side with a crit can really mean a lot of control and, with good positioning, a Rexxar that is building even more +1 counters! 3-1-6/7 is where it becomes really insane.
The Trolls with Rexxar also looked good and is probably a lot better vs Mortimers then you would expect. The amount of healing the team does truly counters DoTs and the amount of Armor makes Jhuroon a lot less dangerous.
Shame the teams don't look Worlds Scenario Worthy.. then again, a Rexxar stalking the woods with 1 or 2 counters will really force your opponent to avoid him.. It may actually be a good one for the Constructed part of the Worlds :-P