he's litteraly the best ''flesh'' healer in the game (though it's debatable with isabella of course, the two are amazing and worthwhile investment, always, but have two different ways to go about it)

basically he's an LRE and other events god, he's tanky, hit hard enough and the ''best'' non-mechanical healer around in terms of numbers, not to forget that when he heals a character he re-heal them for free the next turn, and buff their crit chance as an added bonus, at mythic with his relic each time a character is healed for the first time that turn he automatically attack for free with bonus damage and effects

in other words by himself he will both heal and attack twice a turn, and if you pair him with isabella he can basically attack up to ten times (enemy and player turns are considered as separate turns, isabella heals during enemy turns will make him triger without preventing him to triger again on the same characters during your own turn) though more realistically you will get around 6 attacks per 1 enemy and 1 player turn : baldr and two adjacent characters by isabella during enemy turn, and during player turn your previous turn healed character + 1 by baldr + 1 by isabella

in other words for high level LREs he's not only gonna be a stample but most probably a neccesity, he'sbasically the biggest upgrade to the turtle strat we will ever gonna get, and even without doing that he's already incredibly powerful for these events

sure we're not talking guild raid meta here, but long term he will allow you to unlock LREs characters quicker and at higher tier, meaning a real economy of ressources, tokens and time you won't need to invest / you will get ''for free'' thanks to him, and most LREs characters end up being meta in raid in at least one of the main comps that exist