252 Atk Life Orb Persian Return vs. 0 HP / 0 Def Simipour: 211-250 (72.5 - 85.9%) -- guaranteed 2HKO
252+ Atk Slow Start Regigigas Return vs. 0 HP / 0 Def Simipour: 156-184 (53.6 - 63.2%) -- guaranteed 2HKO
It still hits almost as hard as Persian, and Persian is decent. Also Gigas is a great disruptor, spreading Thunder Waves like a champion. And don't forget Substitute! Due the amount of NFE Pokemon that reside in FU, Regigigas can get a Sub that won't likely be broken in a single hit in most of the time. Not forgetting that it's very easy yp stall Slow Start with a Sub either. For me Regigigas should be A, but I'm not sad with it at A-. It's MUCH better than Swanna, Luxray and Solrock in the current metagame.
20% difference is not close m8 :]
as for the Hub, the Speed-tier is broken ( some examples in bold)
718 / Swoobat / 114 / +Spe / 252 / +2
578 / Sawsbuck / 95 / Neutral / 252 / +2
538 / Articuno / 85 / +Spe / 252 / +2
534 / Ninjask / 160 / Neutral / 252 / +1
508 / Electabuzz, Rapidash / 105 / +Spe / 252 / +1
502 / Carvahna / 65 / +Spe / 252 / +2
498 / Kingler / 75 / Neutral / 252 / +2
496 / Simipour, Simisage, Simisear / 101 / +Spe / 252 / +1
446 / Huntail / 52 / +Spe / 252 / +2
442 / Articuno, Golduck / 85 / +Spe / 252 / +1
433 / Gabite / 47 / +Spe / 252 / +1
426 / Staravia / 80 / +Spe / 252 / +1
424 / Whirlipede / 47 / +Spe / 252 / +2
419 / Ninjask / 160 / +Spe / 252 / 0
403 / Golduck / 85 / Neutral / 252 / +1
398 / Beartic / 50 / Neutral / 252 / +2
384 / Fraxure / 67 / +Spe / 252 / +1
376 / Carvahna / 65 / +Spe / 252 / +1
370 / Krokorok / 74 / +Spe / 252 / +1
also +2 252 neutral Golduck is a thing as RD+SS duck is one of its best sets atm
Also atleast the A+ and A ranks should be in the threat list IMO