One more high-leverage reliever is needed. The playoffs are a different animal and tight games are likely to require more than 9 outs from the pen.
Gelb hit the nail on the head with Alvarado's use - I think that has been consistent over the past couple of years, he will be used differently in the postseason in high-leverage situations to face LHs whenever that may be. I don't think he needs to be fixed - he is best used this way. He can get out top LHBs, but he is mediocre against righties.
Hoffman has been great this year, but the Phils haven't handed the 9th to him. Of note, he traditionally has been stronger in the first half than in the second half; anecdotally, this is what I recall about him last year (I may be misremembering). I also have my concerns about him facing the type of high-powered lineups you see in the playoffs late in the game - he hasn't done this. Last year the Phillies let him do it once - and he blew the save in the 8th against the Braves. That was the last time he was put in that type of position last year. Against the D-Backs he was coming in in the 4th, 5th & 6th innings.
Strahm has always been more successful against RHB and that split is exaggerated this year. We definitely need another top-of-the-line guy to get lefties out.
If I were Dombrowski I would not hesitate to give up a top guy(s) not named Painter (or maybe Miller) to get a top-of-the-line reliever. Then roll with him, the three above, and then Soto and whoever is hot between Kerkering and Seranthony can be your one or two out guys to close out an inning if needed R on R or L on L. In the playoffs, I am not trusting any of them to go much more than the minimum allowed.
Closing out games in the playoffs is how you win a World Series.