Twinks can have larger hp pools due to rings like the Ring of Favor, Life Ring and Prisoners Chain. But note that armor in this game is mostly Fashion, so his armor shouldn't cause you problems.

I'd argue Twinks are more likely to be set up to deal a crap tonne of damage using the Hornet Ring and such, basically insta-killing any low level host they encounter. Also, true Twinks tend to have the fully upgraded flask. What you encountered isn't the worst variant of Twink, but it requires a lot more effort to get the Estus so it isn't as common.

Perhaps From could add some sort or Ring matchmaking that stops people wearing +1 variants of rings interacting with those that don't have access to them. But of course this can cause problems with matchmaking since people in NG++ will have to unequip rings to find partners.

It's not an easy fix, but twinking weapons and armor isn't as much of a problem since often there aren't direct upgrades for these items. If From wanted to fix Twinking they should probably target Estus since I feel the Estus is the worst offender in Twinking. Perhaps Rings should be taken into account, but like I mentioned it can cause problems with NG+ people.