I'd add Morrissey to that group.
He's quiet but extremely valuable.
My playoff MVP's so far:
Buff. He's been utterly dominant. Just dominant. Playing a smart, conservative game with occasional amazing offense contributions, all while utterly demolishing people at every opportunity. Playing against this guy must be absolutely demoralizing.
Helle. Excellent throughout except for a blip, and a spectacular performance to help us snag game 4.
Schief. Had one quiet game but for the most part, with 4 g, he's looked awesome against tough competition. Guy can get an elite shot off in traffic, while playing a smart all around game... pretty valuable in the playoffs isn't it?
Connor. Hasn't been on the score sheet outside of one assist, but I am loving this guy's game. Hardly makes a wrong move on the ice.
And Morrisey has just been consistent and smart as usual.
Guys who have been good but I think there is even more to come from them next series:
Laine. Lowry.