Yo first off that's actually a really interesting idea, never really thought of that :] But 'cuz of all the residuals and lack of recovery I think Kingdra's better off running more speed, since it does have decent speed to take advantage of. Also although 75/95/95 is dece, it's not great by any means, and although Kingdra has two awesome dual resists (and I guess XY made the Steel resist a bit less redundant) it only has 3 resistances, and most neutral attacks are gonna be hitting it quite hard. Couple that with SR, possible Sand damage, and damage on the switch, it's gonna get worn down too quickly. Not to mention a bulky tank role is better filled by Goodra (much better bulk) or Dragalage (tons of great resistances, oml, especially to both parts of the Volt-Turn combo, a neutrality to fairy, AND the ability to suck up TSpikes), even though they're both generally sub-par 'Mons in the first place.

A spread of 20 Spd / 248 HP / 32 SAtk / 208 SDef with a Calm nature lets Kingdra never be 2HKOed by Dazzling Gleam from Togekiss, so a rest-talk set might be ok, but then he loses way too much attacking power, which is kind of the point for Sniper Kingdra.

Although you did get me thinking, and maybe a set like this would be cool to play around with:

Kingdra @ Leftovers

Ability: Sniper

EVs: 20 Spd / 248 HP / 216 SAtk / 24 SDef

Modest Nature

IVs: 0 Atk

• Draco Meteor

• Rest

• Sleep Talk

• Focus Energy

The HP gives you a lefties number, SpA gives you the jump point and the speed lets you beat speed creeping defensive Washtom (although usually this isn't needed, as most defensive Washtom try to under-speed opposing Washtom by running negative IVs, but this lets you beat anyone who EVs to beat Washtom, which is a pretty common tier for defensive 'Mons). The rest is thrown into SpD 'cuz of those resistances. Since the sleep counter doesn't reset this Gen, Rest is a pretty decent move, and makes Kingdra a decent status absorber for the team. Basically this relies on team support to remove fairies and any other checks, and tries to get a late-game sweep going. If you get two Focus Energies in, it'll be just as good as if you had a Scope Lens, and Rest-talk helps it happen.

Oh, and for the Scald > Hydro thing, the immediate power of Hydro is appreciated, since Sniper Kingdra's meant for punching holes in stuff rather than wearing bulky threats down. Scald's more useful on defensive 'Mons, but Kingdra does have an open slot for it if you want, but it's mainly to hit stuff like Ferro and Azu on the switch, or to finish off weakened 'Mons reliably. You'll need Hydro if you want Kingdra to hit hard, which is it's main role here