Brutal during Act 4, but usually actively beneficial during Act 5 since it causes exhaustion before the investigation phase, and so turns off attacks of opportunity (extremely relevant if massive, and also for retaliate). This is due to the "attacks as if it were the enemy phase" wording.
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Q: If an effect causes an enemy to move/attack "as if it were the enemy phase" (e.g. Dhole Tunnel, Myriad Forms), does the enemy exhaust after doing so? (The wording on Ravages of War [from War of the Outer Gods] implies that, without such wording, the enemy would indeed exhaust.)
A: Yes, with the rules as written, if an enemy attacks “as if it were the enemy phase,” they would have to exhaust after performing the attack (unless otherwise specified). Cheers,
MJ Newman