Arnott alternates between being dominant & invisible. He had a solid season, his best pointwise in a long time. I personally think he never fully recovered from that groin injury in the last few weeks of the regular season & it effectively made him a nonfactor from then on out. Same thing happened last year in the playoffs at the end of the Edmonton series.
The most significant thing about him this year is his line was consistently the best line for the Stars for stretches at a time in different combinations (Barnes-Arnott-Morrow, Guerin-Arnott-Morrow, Ott-Arnott-Oliver, Guerin-Arnott-Bure), accounting for a high +/-.
His biggest flaw will always be inconsistency. Re: his contract, I really don't believe the Stars will qualify him, but they will probably try to resign him at a lower price as a UFA. Earlier this year, he had really good value but it's been kind of overshadowed by both his & the team's overall playoff performance.