For everyone except maybe the three Easter Ring 2016 owners (on some mobs and/or events), even the 600-700 PED Improved Ares is a better right hand ring in pretty much all situations and it's explained in two words; Focused Blow.
Just for sake of comparison let's use a fairly common ul sib combo, M83+impA105:
Easter 2016 + MMOWC: 3.112 dpp, 81.389 dps
Easter 2016 + Imp Ares: 3.131 dpp, 81.888 dps
The -16% crit dmg (defense), 16% acceleration and +30 HP of MMOWC do help in some situations, mainly events, but in most situations Imp Ares is superior to MMOWC even for Easter Ring 2016 owners. For rest of playerbase (all but three people...) there is no question really. The secondary (defense) effects, which in general are far behind dpp affecting buffs in terms of importance to net returns anyway, can be replaced by 1.5k-2k PED Modified Athenic (-16% crit dmg, 16% evade/dodge/jamming) and/or 150-200 PED Modified Hermetic (15% acceleration) to fit the occasion (ranged vs short-ranged hunting).
A stable of Imp Ares (600-700) + (1.5k-2k) Mod Athenic + (150-200) Mod Hermetic comes in at around 2.5k PED. Them automatically being combined and together with +30 HP with MMOWC, I suppose there's an argument for like 4k PED for MMOWC (at the most!). But you still miss out on the ever important dpp edge Imp Ares would provide. Most reasonably enlightened hunters wouldn't even want one.
I guess we will see what actually changes in terms of importance to returns with the 2.0 system, but that can be said for all items. As of now, MMOWC is absolutely not worth more than 10k. If someone bought for 20k or above (which is doubtful to say the least, screams a lie) that's overpaying immensely, grats whoever lucked out with that sale. I'd even say Linzey's 11k sale is a good one.