While I agree that attack is an important stat, I disagree that It needs to be fully invested in too. His attack stat is really only raising the percents past the already OHKO marker on most pokes, so you dont necessarily need to continue boosting attack. As long as he can reach a healthy amount that still allows him to get his OHKO's, 2HKO's, etc., then his attack stat doesn't need full investments(similar to many other sweepers that don't need to invest in as much attack, like Bulky Gyara).
With that, running a bulky set with Adamant nature can cure the need to place so many EV's in attack, allowing to already have an edge on most with just his nature alone.
When it comes to speed, I think the lowest I'd ever go is 261, which is 124 EV's with adamant nature. With all the newer pokes, spe is still a major factor. while 60 spe is still relatively safe, it still misses out on his major counter that'll be lurking around: Scarfchomp. Even with Haban berry, it'll likely K.O if your around 60-70% health, unless you place a decent amount of EV's in bulk, which you may not have by investing a good portion into attack.
IMO, this set still accomplishes proper OHKO's, and the like, with SR assuring some:
Ononokusu @Haban Berry/Life Orb/Leftovers
Mold-Breaker
Adamant Nature
176 HP/74 Atk/146 Def/124 Spe
-Dragon Dance
-Outrage
-EQ
-Taunt/Brick Break/Dragon Tail
Still reliably 2HKO'ing Scizor all the time after 1 DD while taking 45-53.4% from a CB Bullet Punch. It can also still OHKO Jirachi, and make ScarfRachi even more setup bait, taking only 30.3-35.9% from Iron Head, and Ice punch being able to 4HKO, or possibly 3HKO. Skarmory's brave bird is lessened to 32.3-38.3%, and gives you a free DD, in which your damage begans to outpace it. Gyro Balls also dont hurt nearly as much, even after a +1, helping with that previous problem.
I could go on about that set, but the main point is that with that bulk it makes up for it's attack just as fast by allowing for more DD's. Life Orb can also be used in that set, closing that gap of attack power immensely.