Well, this will be interesting to watch. If Arians loved Heath Miller, he's really going to love Howard. I think it is safe to say his days of only playing 60% of the snaps are over. Arians appreciates good blocking from the TE and he leans heavily on the vertical game, so hopefully he's able to fully utilize Howard to keep the defenses guessing. Howard is coming off back-to-back (albeit small sample) seasons with 16.6 ypr. He'd be crazy to waste that.
I think we really need to dig deeper into the stats to paint the full picture about Arians and his use of TEs:
From 2007-2011, PIT ranked 26th in pass attempts. When Arians started, the team still had the "run the ball and play defense" mentality, however, passing attempts increased in each of his seasons, going from 442 to 536, despite having the #1 ranked defense in his last two seasons. During that span, they ranked 25th in TE targets, so roughly in line with total pass attempts. As the interim HC for IND he ranked 5th in pass attempts and 13th in TE targets despite only having a pair of rookies to throw to. During his tenure in Arizona, they ranked 10th in pass attempts and they ranked 31st in TE targets. The top 3 over that span were Gresham, Housler, and Fells. So to me it seems he uses what he's got. And given that he had Michael Floyd and John Brown, two very good vertical threats when they were playing (not drunk or injured), to go with Fitzgerald, he really had no need to go out and get a receiving TE given he ran 3WR sets almost all the time.
Of note, from 2012-2015, PIT again ranked 25th in TE targets. The only difference is that the league as a whole was throwing the ball more. The team ranked 10th in pass attempts over those 4 years. So as a % of the offense, the TE targets actually dipped during Haley's tenure as compared to Arians. So it wasn't that Haley was good for Heath and Arians was bad. It was just the larger volume of passes during that time frame (589 PA/season vs. 498) that propped up Heath's stats compared to his time with Arians.