I use (used) Ello's Band, mainly because I use 2 elemental force enchants and stack haste. More crits per proc. At that level, AP isn't the big BANG it has been traditionally, since we lost crit from agility, hence the elemental force is doing the major majority of my damage. Sure, the 1 extra AP will give you a bit extra dmg per hit, but...
Assuming you swing 4 times in 3 seconds, that may be something like +4 dmg vs elemental force 1 proc every 3 seconds at 110-220 non-crit / crit.. you can see that extra bit of crit chance will make a nice difference when your enchant procs.
EF has a real proc per minute stat of 10rppm times 2 if you use it on both daggers. 60 seconds / 20 =3 so ef procs roughly every 3 seconds. Due to the rppm, EF MUST proc 10x in 60 seconds.. (big formula that i dont get, but it works) lol