Well if the conversion for DEX in 2 handled weapons are .75 then 3 DEX is 2.25 so 2 of this rings will be 4.5 acc rounded down to 4 they are not bad before 40 when you get a nice ring of acc giving you 5 in one slot :)
Souske - not so true. MNK (and maybe other classes) gets an extra bonus to DEX. MNK gets 2 ACC for every 3 DEX. That would be a total of 4 ACC for 2 of these rings.