Depends on the game, the first game had Dia as the undead nuke. But that's also irrelevant, this is FFXIV, a modern tab-target MMO, not IV or X. A lot of older WHM were also SMN, so they still had access to rather powerful nukes. Likewise, in most previous FF games with a job system, WHM is the counterpart to BLM; restorative vs destructive, light vs dark, etc. Both were casters that specialized in big numbers, low health, and being overall squishy. Having WHM being the healer version of BLM makes sense, and adapting BLM style mechanics to a healer like WHM would possibly even convince people who enjoy BLM to try out WHM.
It's a poor proxy because some jobs will go through stupid lengths to gain a few extra points of potency while others are more or less optimal without too much effort. Again, you'd be suggesting that NIN is as hard as SMN because it has a similar gap. As far as I'm concerned the logs only really tell how punishing a job might be if you mess up, but it doesn't tell the full story behind each of those fights or how hard a job is to master. It's not a good metric to use for that.
It's why I tend to say "engaging to master" rather than "hard to master". I don't consider WAR hard to master at all (although I fully admit I haven't taken it into difficult content this expansion, someone else can go over larger details on getting the most out of it), but I still consider it good fun and it has things to watch out for. Besides, Infuriate being reduced with every Fell Cleave means I have something to watch out for before I commit to a Fell Cleave, in that sense, I'm not "reacting" to it after the fact, I'm contemplating it beforehand, I'm planning out my usages of Fell Cleave and Infuriate so that I don't accidently overcap either the gauge or cooldown. What does WHM have that is similar? That I press Dia every 30s or that I have to watch Assize? These things have no interaction with each other and aren't particularly engaging or fulfilling. They're boring, they don't lead to anything else. Fell Cleave at least leads to me using Infuriate more often than not using Fell Cleave.
There's certainly a lot of people who seem to think like me then. Either way you're not doing a good job of convincing me or them.
Like I said earlier, it's a terrible proxy and doesn't tell the full story. At most it tells you how punishing a job might be to play poorly, not how hard it is to play well.
I need more context behind what you mean by this. Are you correcting the numbers, or are you saying that it should only be 1% between optimal and non-optimal? If it's the former it makes your argument against Roe worse, if it's the latter, then there is no common ground and you make playing well vs playing poorly meaningless. It'd be like telling your best worker, the one who shows up on time, works overtime, has incredible knowledge in his field, that he only gets 1% extra pay compared to the guy who shows up late, screws up basic things, and leaves before everyone else clocks out. It's downright insulting.
That large range includes players who legitimately don't offer anything to a fight and skew what would be average play up to above average. Extremes sets a skill floor that everyone has to meet or they fail, casual content doesn't. That's fine for casual content to lower that floor considerably, but it's poor for assessing how a job is balanced for unskilled play vs skilled play because you now make "not playing your job" a viable tactic for an odd party member or 2.
Also again the gap doesn't matter, it's only smaller because the floor for clearing is higher.