Depends on the players you bring in but the only key player you're really missing is KDB. And bringing him in (and/or a second City defender) would leave you stronger for the GW19 too, as well as for their excellent fixtures afterwards (wba, SHU, bur). So it's not like those transfers
only count for this week. Ditto United players, who also have a double and decent fixtures beyond that.
Given that, you might be able to get more value from using the FH in the later blank GW in 29. I believe (unless things have changed) there will be a DGW26 and those double gameweek players will then blank in 29. For people who have used their FH already that would probably mean wildcarding before the DGW, having to include a good few SGWers, then using the subsequent fts to transition to a blank gameweek team in 29. Whereas you'd be able to commit entirely to the DGW where they won't, use the subsequent fts to target non-blankers they can't afford to bring in and then FH in a blank team that will probably beat theirs anyway.
To my mind the value of all that outweighs whatever disadvantage you're at this week. At least that's the way I was planning out my team before I lost three Villa players.