A muddled situation, to be sure.
First, Armstrong wasd retained, but there's no guanrantee he will coach ST; it might be one of the others, and he might do something else. Or, Saban will have more coaches, such as maybe having a ST coach, but still having Armstrong work specifically with the returners, or the blockers, etc.
Second, I think the Phins ST unit has been an overall disppointment in the time since Westhoff left. They seem to do well on coverage; they get downfield fast and tackle well. But the thing I see other teams do all the time that I don't see from the Phins is establish a blocking wedge; when the retruners here get a good return, it seems to be more by accident than design. There isn't that dominant consistency, that sense of a plan in place that I see when I watch other teams' returns.
Third, I'm sorry that this is going against the popular opinion -and I don't mean to be a bummer on what emerged as a possible bright spot on the team late last season - but I don't think Welker has the speed to be a true top-five return guy in the NFL. He has some moves, some elusiveness, but when it comes right down to it he makes big returns on blown coverages and misdirection. He's not a guy we can count on to get a seam and take it in because no one can catch him.
I could be wrong about him; now, watch him score repeatedly next season and make me wrong - which I would LOVE; but I doubt it. I just don't think he has that straight-ahead burner's speed that you want in a top returner.