Why is the next new job a melee DPS?

[Vyrerus]

You always end TenChiJin with Suiton for single target.
That's what Meisui is for and why it lines up with TCJ's cooldown.

No fight in which you have an assigned ranged position, actually needs to stand at a distance for the entire fight, only for specific mechanics. Which is what Raiton is for.
In fact, all players should be within melee range for most of the fight anyway for AoE heals.

Meisui didn't exist in Stormblood, and the potencies of Ninjutsu were different.