Also, if you're under the assumption forsaken thoughts will shave off some of the positive damage you're vulnerable to - get that idea out of your head because it will not help you.
The only pure damage reduction legacy is gates, and having had it on numerous characters I can say a lot of the time there's a better option.
So, the key to warriors is to put all your chips into one aspect of whatever you're trying to do.
Want to be survivable? Go all survivability class/legacies for maximum synergy.
Damage? Highest DPS classes/legacies, etc.
Examples for this would be:
I'll base one off your example - dagger/flail duergar
So you have hamstring(-dex), bleeding, statloss, and the ability to remove dodge with entwine. You'll be taking a lot of damage vs. other smart warriors before you get off enough skill moves to be scary.
hurl, hamstring, entwine are not easy to get going and fail often compared to say - bash spam, cranial spam, etc.
Whispers and defender powers will help you outlast people but you'll have to put distance between you and them to make it possible, and that includes not succumbing to lag.
To pull of your build as an example I would recommend harmonious to not get locked down and to stay mobile. I would also change the race to arial who have a TON of built in evasion and with higher dex you might actually pull off a lot of these skill combos to be lethal. You trade vulns but arial is actually easier to cover the vuln since water and lightning are not as common. At hero level play you should be able to get items that have built in vuln reduction. With either race you will be eating that vuln damage at low levels. Thems the breaks.
For PvE dagger and flail/whip are not the ideal tanking options but you will have a lot of utility with pull and choke.
Again, if you have never played a warrior before - this is a huge leap in tactics to pull off if you're not familiar with the groove you have to be in to pull it off.
For a little easier time there's this...
Duergar has the ability to do a ton of damage and I've said it once and I'll say it again: damage is king.
There's nothing more fun than sword/mace chilling/cry duergar berserker. Spam cranial on everything and win or bash,trip, dirt and flurry everything and win. The choice is yours. Also, you'll melt everything in PvE so there's that.
Both builds require getting a mage kill, and if you have high enough damroll you should be able to one round any dark-elf mage at around 11 when you use mithril weapons. Same for elf and iron.
If you have more questions don't be afraid to ask!