I agree they're not likely to just pull the plug on Nick, let alone be prepared to pencil him entirely off the roster next season. But getting a decent trade deadline OF still doesn't have to mean that (or only that).
Simply upgrading from Pache gives you a RHB you can play in LF with Marsh (because that isn't Merrifield either, I'd just give his job to Clemens, but that's a whole other issue).
Or if you make a significant upgrade who is either a LHB or good from both sides, he could play RF against some RHP, and Nick could also play LF against LHP.
But also, sure, if Dahl locks down a roster spot great. Almost no chance they do any trades until after the All-Star break, and for a guy like Tucker probably not until July 31.
Does Dombrowski really have a history that is germane in the here and now? I just don't feel like his moves as Phillies boss have been "go big or go home." Marsh was an outlier and not even that big a move (he had cost, but from an area of depth, and Marsh wasn't even a proven player, that was more like a swap of two young guys). He has that history at previous stops but he has not resembled that GM here. Trading for an OF last year or a better relief pitcher than Robertson the year before likely wouldn't have changed the October outcomes and I doubt that's the case this year either. Being a 100-win team makes it more tempting to go big but at the same time, big deal are more helpful for pennant races not the post-season (unless you don't have three starting pitchers).