I really doubt your resolve
If you increase Stamina even more, and decrease others except hiding to 0.3, who in their right mind would not want to be a pure Strength Tank?
I could argue the importance of Aiming and dodging, why these 2 skills wouldn't be increased if the aim is to lower HP ?
If you increase the exponent, then you need to have less skills in stamina and hiding to make them effective. That way, players could afford not to put their AP into strength and move the AP elsewhere, thus reducing the HP at the same time.
I really think that stamina and hiding should either be removed totally, or change stamina to shooting which is very similar to Zeta's suggestion.
The other option is to change the formula so it isn't attack / defence and make it aim / dodge and redesign the formula so that aim and dodge are more significant. That way players would be inclined to create a split dex / mob build for fort fights and then they can choose to be one of many builds:
Sniper - more dex build - somewhat lower hp but high chance of hit / damage
Dodger - more mob build - somewhat lower hp but higher chance of dodge / resist
Balanced - fairly equal dodge / aim
HP - more str build and hp - less overall effectiveness.
This would then also allow the development of hard hitter and resistance builds with the new damage formulas, thus making many, many options for fort builds to mix things up a little and bring back more diversity to the game, whilst allowing many of the semi-fort fighters/ job / questers to participate with effective builds, thus getting quieter worlds to fill fights.
Tactics could then be brought in to give even more diversity and the only AP with only 1 skill would be strength to reduce the dependence on HP builds and tanks.
The problem at the moment is aim and dodge are almost worthless so nobody bothers to add any sp to them as they can still hit for 60 off the floor! Make aim and dodge way more important so players have to include them if they want to be able to hit a barn door or avoid being hit.