How you should expect to play warriors
First off
Let's get TANKING out of the way
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1). If you think warrior is NOT the WORSE TANK you are sadly mistaken, warriors are complete dog **** at tanking raid bosses. They strive to tank and block MILLIONS of damage from SMALL AMOUNTS by BLOCKING that damage. Simply put warriors are the best tanks to take a lot of damage distributed from small damage sources and throw that **** away. When it comes to BIG D DAMAGE that's when WARRIORS TAKE ALL THE BIG D. Warriors have absolutely no talents that help much vs raid bosses in comparison to other tanks.
2). Warriors should NOT be played as tanks. If you want to tank because you can equip plate gear then go ahead, do that **** on icecrown where you get x7 experience, you can hit lvl 80 within a day and get 6k gearscore within a month because the bosses are so easy fresh level 80's can kill them. Play on lordaeron with the big boys to learn what real raiding is about. All of the content is difficult and tanking as a warrior requires some seriously strong class knowledge, good gear, min/maxing, and learning when to utilize your cooldowns.
3). Anybody, can tank anything, anywhere, anytime, on the Icecrown server. Lordaeron shows you the truth behind every class and warriors are by far the worse class to play as tank.
4). You're a GOD at tanking dungeons though so stick to that for tanking and leave raid tanking to the real tanks (unless you're overgeared/know exactly how to do it/are on icecrown server)
Now that we got the ridiculous thought of tanking out of our way let's move on to what we were born to do
GODS OF DPS/DAMAGE
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1). Yes warriors are by far the absolute BEST dps class in wotlk with firemages coming in close behind them
2). Explaining armor penetration
-First off sunder armor always increases your dps and you need it even if you have Arpen cap (1400 arpen doesn't remove all armor from boss)
-Second, you still need to use shattering throw from combat stance to increase your own dps AND the raids dps
-As a warrior you should be applying both sundering armor stacks and shattering throw to the boss to remove as much armor as you can for not only yourself but also your raid AND you benefit from both even if you're ARPEN CAPPED because arpen cap DOES NOT remove all armor from the boss
-Do not Gem for armor penetration unless you are capable of reaching the armor penetration cap with ease and/or you have enough strength and flat damage to make doing true damage worth it. Also take note that there is food that can give 40 arpen AND an elixir combination that gives 45 arpen + 20 all stats (20 str, 20 agility)
3). Gear: Most of your gear should give arpen + crit, some of your gear should be agility gear that gives agility + the 3 stats of attack power, crit, arpen, so you can reach high numbers for by having double crit from items, maintain the attack power you normally would get from strength gear, AND still easily achieve the arpen cap
Pretty simple, you should stay focused on being top dps as a warrior, collect tank gear so when you're 6k gearscore dps and tank you can tank easier content for friends and **** and still be focused on being the #1 dps in the game when you're clearing content as you won't be the best tank around.