He would certainly make the team better but I'm not convinced he's fine (and neither were the Red Sox). If he wants to take a one-year deal, sure, great, but the problem is you can't pick up money trading Hunter or Neshek or Nicasio without it still counting against your tax and nobody would give you anything for them knowing the situation.
I don't go into the tax - or even give up the 3rd rounder - for a relief pitcher unless he's a steal. And while he's surely not getting that six - or even three - year deal he wants, you probably still have to beat the QO (which either means $18 million one-year or $30 million two years). Also, while this could also change, supposedly Kimbrel wants to close, period, and that's not a good fit for the Phillies with their depth (or good strategy).
I think a reliable LH starter, even a 4th or 5th starter, makes almost any team better than an extra bullpen arm, but it definitely makes the Phillies better.
I wouldn't touch either of them though unless it's bargain basement. Save the $ to pick up deadline acquisitions.