After considering the excellent gains that can be had from +affliction rate, I've invested in maxing several Rs and 1 SR and equipping them on my debuffers. My Cthulhu now has +6% affliction rate, providing an accuracy bonus to all 4 of her debuffs. Maxing Rs is a lot cheaper than SRs and SSRs, and the affliction rate bonus helps the entire team. I may forgo SSRs entirely and just find SRs with the bonuses I want, as SSRs are too rare to have much of a choice. SSRs stacked with ATK can be strong, but since every character in my team has a useful stat debuff, I'm not convinced the added ATK is worth the investment.