The introduction of the Reflect status effect seems to spell the end of farming The Warrens faction on a daily basis. This is going to be quite a blow for many players.
One of the troops in the final battle is able to apply Reflect, sometimes to the whole opposition team. The resulting damage will kill Skeleton Key after one or two casts (probably just one, for most people).
Waiting for the effect to be broken (with an enemy cast) is, at best, going to multiply the time for the final battle by a considerable amount (at least triple, maybe as much as x10). At worst, Reflect will be reapplied multiple times, leading to a likely loss.
I haven’t looked into which troop gave Reflect or how often it might happen, but just the fact that every troop got the same effect is a nightmare.
I’d like to emphasise that this change is likely to affect mid-game players the most (and everyone moving into mid-game from now on). I say this because late-game players probably have enough Chaos Shards that they no longer have much reason to farm daily delves. There’s a calculation I have in mind, but the short version is, if you do every Tuesday Faction Event, and don’t try to raise your Hoard above L100, you should naturally generate close to the 8000 Chaos Shards usually needed to get 4x Mythic troops on each new Faction, without needing to do any Daily Delves at all. That’s a lovely drop in work-load!