So, Jalter, even without Merlin, is still incredibly powerful. The synergy of her skills makes any unit that can buff crits REALLY power her up. The crit damage up + star weight up skill is REALLY good in conjunction with the buster up skill, so if you can get her and a Merlin support, or maybe a Waver support, you can really steamroll a lot of fights in the game. In addition, being that she's an Avenger, nothing can actually resist her in NA right now, and she also gets a 1.1x attack multiplier on her attacks because of her class, making her ideal for taking out really beefy Berserkers. Since everything in NA only has a single life bar, Jalter just cleans up house when it comes to any and all fights that have only a single boss unit.
I'm just sitting around with 300+ quartz, waiting for MHXX to be rollable on JP rn.