I actually have seen 3 of his games this year and well, to me, he did not look dominant. Nowhere near, actually. But those weren't necessarily his best games. However, statistics support the eye-test. What he did in both NHL and AHL is nice and all, that's why there was never a question he is going to be a good player for Graz. The question was how good. And well, "good, not great" is the answer. He isn't relied upon much defensively. He is 3rd on the team in faceoffs taken strongly supporting the argument he is the team's 3rd center in TOI (albeit Graz often rolls 3 lines). He is one of the 4 top scorers on the team which, again, is good but nowhere near special.
I'm not saying Rasmussen is a bust much like I wouldn't have said Raffl is a sure-fire NHL player when he played in Austria. It's more nuanced than that. But he, even considering his age, has very obvious limitations as to what can he become (or not become) at the NHL level.