The biggest issue I've experienced so far is the lack of passive Mettle generation in longer fights. If there was some form of mettle refunding or way to trigger Revel in Victory mid-fight many of the DPS issues would resolve.
The issue is with stabilizing the baseline, the damage itself isn't bad the issue is the drought when Get Serious is down or Battle-wise just doesn't want to proc. As it is I would say the damage is closer to burglar range than say Champ or Hunter. I know it may different at later levels with LIs and traceries but just from experiencing the class without LIs and comparing against other classes the mettle is just the big speed bump in the whole experience.
The issue was similar with tanking pre-buff pass. The biggest issue I experienced was attempting to recover after going down on a boss fight. The overall experience is a bit dampened by a momentum loss whether from bottoming out on mettle or not being able to re-establish aggro after dying when tanking. The latter issue seems to have been resolved so bottoming out on mettle just dampens the experience.
Wrecks 50 Beorning | Treebeard
"Remembering that you are going to die is the best way I know to avoid the trap of thinking you have something to lose. You are already naked. There is no reason not to follow your heart. ... Stay hungry. Stay foolish." - Steve Jobs, RIP-