I think a good way to change the stat contribution would be to have Tank Damage based on both VIT + STR but with less weight on STR.
If we take the example of current gear and a 3:1 STR to VIT ratio in the damage calculation, we'd have:
- il210 Fending accessories would contribute 49 VIT in dmg
- ilvl150 pentamelded would contribute 29 VIT + (32/3 STR) = 39 primary stat in damage (which would be equivalent to an ilvl190 VIT accessory)

That way, VIT accessories are the clear winner for tanks but Pentamelded ones are still relevant as a stepping stone without being OP.

This would be fairly easy to implement and wouldn't require to completely revisit earlier gear.