My take on superalloys is drill as deep as you can, keeping the cutting action going. Obviously if you aren't using TSC you're limited, but each retract/return is (as I said) another chance to initiate work hardening as the drill tries to reenter the metal. If you can cut the number of pecks in half you'll be ahead of the game.
Try to balance the speed and feed to keep the chips coming out of the hole, some experimenting is needed. 50 SFM should be within cobalt's range in 718, at least try it.
At .34 IPM and 15 SFM, roughly 190 RPM at guesstimate .3" drill size? That's less than a thou per tooth, I think you're rubbing too much. Try a more aggressive cut, .003/tooth or so. But start with a fresh drill, not one already used on a slower cut. If you can use a stub drill and avoid spotting I'd do so.