Don't get me wrong, both Rain and Lasswell have equally boring skillsets and they're already 5*.
I think it's just more symptomatic of the granularity of the game's balance in general. Abilities are very, very distinctly better or worse comparitively to one another, which goes back to a core weakness of the design of simple turn-based combat. When you have one action, and that's all you can do till your next turn, abilities tend to get compared as-is, with not nearly as much nuance or opportunity cost balancing to keep things in check.
I mean, yes, there's everything from AOE vs ST, to element vulnerabilities, to element chain and spark chains, to buffs and debuffs to consider, but it still really boils down to the basic gameplay loop of one action per turn. That's it. No opportunity cost modifiers like e.g. Bravely Default's Brave/Default system, nor cooldowns in Granblue Fantasy (just to pull from two very similar turn-based combat setups)
This is why Barrage is far away above all other current physical abilities. This is why Full Break is essential. This is why Dual Wield has virtually no other peer in usefulness. They tower over all other alternatives as the underlying game mechanics don't have enough interlocking systems to balance out the opportunity cost. (It doesn't really help that resource is generally lumped into "MP", really)
Characters either have overpowered abilities (or TMs), or they don't. Which either means you've pulled them, or you haven't. The meta in Exvius very strongly leans towards very, very distinct best-practices with little variation in setup, and this is only mildly alleviated with the game maturing (e.g. where Japan is now). This in turn creates an environment where if you're out of luck with pulls, you *will* get brickwalled by (largely optional atm) content.
While we're on this note, I want to say I'm honestly really baffled at the tuning of this Demon Heart event. The stamina opportunity cost for getting a simple 35 stat item is all out of wack when compared to other 31-39 stat items other than MAG. If I could give an analogy, it would be like if a STR item in WoW was a quest reward, while a MAG item of equal strength required you to be Merciless Gladiator or something.
But hey, I guess we do need something to grind, and maybe this is simply Gumi/Alim's laboratory test as to how bonkers people are willing to go for incremental improvements in power level compared to getting lucky and pulling the right characters, and we're all unwitting guinea pigs saying "yes, we'll do it". ¯\_(ツ
_/¯
(Sorry, this is a bunch of personal musings not directly related to Kain or the quoted at all, but I did have to get it off my chest. Felt the same way when playing JP launch)
