From a math standpoint you're going to need to have exiled 5 level 1 cards to break even with this card. Your gains lessen the higher the exile level is too. Basically then, this helps keep Flare and the upgraded coat/keepsake from leaving play. But again, you're going to have to get 5 total uses of those cards to even break even, and I'm just not sure thats a scenario you are realistically going to see often.
I have played this card in Zoey Samaras decks lately has a "placeholder" for Cyclopean Hammer: at the start of the campaign I take In the Thick of It and with the 3 XP I purchase Enchant weapon and with the combination of the 2 cards I can once per round pay 1 action to attack at +3 for 3 damages or pay 2 actions to attack at +6 for 4 damages!
Dexter is a great candidate for curse builds due to his access to Faustian Bargain. Not only does the bargain itself generate a ton of resources, but also curses which the bread and butter Mystic is lacking in options. His investigator specific ability isn't that great, but his weakness also isn't really an issue so that balances.
Overall a B tier Mystic.
The thing that makes this card good is how frequently you want to play it. The central reason you want to evade enemies is so that you can clear clues off locations without having to deal with them, either leaving them to your Guardian or walking away from them entirely. This card does the thing that makes the game progress while effortlessly avoiding the things that stop the game from progressing and mitigating the risk that it all goes sour. Technically it's barely an extra action for 2 resources, but practically it's a stunningly powerful card for seeker rogues and will rarely not impress.
There are so many things great about this card. It filters monsters from the encounter deck and redirects them to your mob handler. It spawns aloof enemies engaged with you, severely nerfing their revelation effeft. It saves the Guardian from drawing a bad card during mythos.
And finally, the upgraded version gives you an off global emergency cache when you kill whatever got stuck with it. Or, if you can't find an enemy, it gives you a pass on the encounter deck.
Use it, abuse it, don't look back.
Edit: Some folks say that forcing you to draw aloof enemies is a bad thing, but I couldn't disagree more. Even though aloof enemies won't be damaging you, they will be hindering you in other ways, especially in the newer scenarios. Generating doom, making objectives harder, etc. Clearing them out is a nice benefit. Even the older cards (wizard of the order, acolyte), forcing them to spawn engaged with you dramatically reduces their game effect.
Mandatory monster handling card imo.