There is no DEX tier. It has never been true and all comes from someone's misinterpretation of Ninjiitsu's data (which no-one else had previously mistaken).

That said, there's no good reason to put bonus points into DEX at this time. STR is superior all around due to adding both damage and mitigation. The question is STR vs. VIT, and that's pretty well solved as well -- people go full VIT and use accessories with both STR and VIT if they feel they can sacrifice some amount of VIT.