Its not hard its unbalanced. The first problem is the poor AI programming that makes every bot a walking Aim Bot with freeze capabilities here. Even the super strong Yeti can run from you, turn 180° while running for couple frames just to snipe you with ice, and then turn back 180° to face the direction he is running again - all WHILE RUNNING. Especially on crazy this leads to a lot of nonsense freezes and deaths from bots that don't even look at you.
The second problem is the Imp-Yeti paradox where both are meant to be close to each other to win but they refuse to. And moving from the Imps location to the Yeti costs all the seconds you will be missing later. This adds a pure random factor and wastes 30 minutes if they are not close to each other and constantly running into opposite directions.
And no; having to abuse the AIs programming is not a valid solution to the problem as AI exploits are a very specific difficulty that should not be the challenge here. Almost all the people i have played with don't even understand the concept of kiting as it requires knowledge of a technical layer in the background.
Not to forget that a "hold fire" scenario is contradicting the ENTIRE design of the game. Which is a shooter to kill things - where to win means to push forward and eliminate targets. And yet the game punishes players for doing exactly that on the Imp and it takes a whole 30 minutes to realize that for 4 people.