PvE Scrapper Tank?
Keep in mind that tanking in gw2 isn’t like tanking in any other game, mainly it’s your job to control the boss with it’s positioning and to deal with his auto attack and call out fields if needed.
I think you’ve gone with the right approach to toughness but you should also be able to get away with knight trinkets and berserker armour, mainly because trinkets are easy to obtain and berserker stats are still prominent in all other aspects of PvE . You should also use a berserker weapon. You only need to have the highest toughness, not really a lot of toughness.
http://gw2skills.net/editor/?vdAQFASlUUhSsYfWwdLQ7FLQIFde+nFaY4MOlzXAENVDA-TxRBABUcBAgUJ4Nq/Qz+D4pDgLlfA8AAAA-e
notes of change
Bulwark – Grenades.
Glass Cannon to Grenadier
Short fuse to Shaped charge
Adaptive armour to Perfectly weighted.
Armour to Berserker
Trinkets to Knights
Added Berserker weapon.
Runes of the Scrapper to rune of Pack.
Runes of the brawler may also be good for you. Scrapper is again good in PvP but the 7% increase when the mitigation is so little anyway, it’s not worth it.
Hope this helps.