I think there is a lot of overthinking. You need strong pitching to win the WS. How many relievers you need is dependent on your starting pitching both in how deep it can go and whether it can be deployed from the bullpen. You also need the pitchers to pitch well in the small sample size of maybe 1-2 games. So to the last post, was Arizona's bullpen better, no, did they pitch better in the series, yes, though to overall note there were 10 earned runs allowed by relievers all series, 4 by Kimbrel, 2 by Kerkering, and 4 spread among 4 other RP. Paul Sewald would then allow 6 ER in the WAS. You want to have lots of arms you can trust so you have the best chance of not allowing a weak spot to show up, but there is diminishing returns based on the number of innings being pitched.
As for the Phillies the guys they have are battle tested over the last two years. Jeff Hoffman may not always have pitched the 9th, but they consistently had him in the highest leverage spots with men on base and/or vs hearts of the lineup. Matt Strahm was scoreless last year and closed out games. Alvarado allowed 1 run last year and carried the bullpen to the WAS the year before. Seranthony Dominguez has struggled but has been absolutely nail two postseasons in a row.
Wanting another arm to spread the regular season load around and to just have yet another arm in the postseason (also they don't really have that many places to add) is fine. I just don't know if looking at their current situation as missing that thing is really accurate and more just grasping.
