From the characters that are out: Klee, Ningguang, Yanfei, onfield dps Mona, onfield dps Heizou and Wanderer possibly for the normal/charge attack buff.
Out of those only Yanfei has a high energy requirement on her burst (80), so she would get the most out of the ER. Her burst isn’t really needed but it’s still nice to be able to use it for the increased seal speed and charge attack damage bonus. It also provides a shield at c4+.
Can’t say how it really compares to the alternatives though. Still should be an okay f2p option, especially if one doesn’t have a Widsith (or hates the rng) and no Dodoco Tales.
I mean you could still eventually run it on Yanfei and give your Widsith to someone else. There’s definitely more Catalyst users who can make use of the Widsith. And as I said I can’t really say how these weapons rank against each other or Dodoco Tales. I’m currently not motivated enough to actually get into TCing.
Overall I am however an advocate for “better have and not need, than need and not have”. Especially with non-banner weapons: There’s 2000 slots for them while only need 1 per character, when we only have 1800 slots for artifacts - of which we need 5 per character… You easily should have more than enough space for an additional weapon.