If you use dlc pack items the game is ****** easy. I literally beat the game with a dw rogue by just autoattacking. Get shadow spec, varric to spam chameleon's breath and fatiguing fog, anders for heals, heroic aura and haste, boost dexterity to 60 (with dlc items and buffs that's about 100% crit), rest to cun and just melt through everything by using nature or spirit mainhand daggers and jarvia's shank for offhand (stats are insane on this dagger).
I destroyed the ancient rock wraith with just autoattacking. Remove tactics by Self:any->wait, hack away slowly till he breaks down, then enable tactics again, load haste, hex of vulnerability, chameleons breath with spirit daggers and spirit staves, and melt him in 15 secs. Getting lightning resistance on you and varric is good too, but optional.
Then get assassinate and 3shot the arishok. With a nature dagger, drop decoy, mark of death, assassinate, twin fangs and load the explosive strike. If he doesn't die he will be left with 10% health. Just spin around the pillars till you have your cds again, and kill him.
I crit the damn genlock alpha for 42k + 21k assassinate and for corypheus fight, got fire resistance for everyone (except bethany, doesn't have rune slots so I used barrier). 1 assassinate gets him down to 70%, so only thing i have to do is to tank the flames, kill the demons, assassinate corypheus, repeat.
Same thing pretty much with sword and shield warrior. Assault and scatter crit for ridiculous amounts of damage and sns actually does more autoattack damage than 2h and it's easier to exploit the movement of bosses to avoid damage due to faster attack animations. It's just the matter of having the right elemental weapons and every single boss fight becomes trivial.
So yea, armor penetration isn't really gonna fix a game that you can exploit and go through armor and through boss tactics. If you want to make it more tactical, make autoattacking a small part of the damage, make skills do a lot more damage but with hard limitations on range and aoe diameter, make boss tactics unavoidable by 1 resistance rune and balance the game around it. Force us to have to move the party away from the aoe and use our skills the optimal time, with stacked debuffs or cross class goodness.