Aw man, really? That sucks. The game is too easy on Expert, but if I'm really just dragging out battles for myself unnecessarily, I guess I may as well bump it down. But I'm level 70 with 146K attack, 3191K armor, and 9245 health regen (or whatever that last main stat is). That's not good enough for Master?
And thanks for the toughness explanation earlier! I think I got what you were saying.
Like I mentioned earlier those stats are pretty much worthless at max level. Damage is just as bad as toughness because a lot of stats are not included in that calculation. The easiest example to understand this is elemental damage. All make believe here, but: say you have 10 damage on your character screen. With that stat you have a fire attack that will hit for 100 damage. Now, if you have stacked 100% fire elemental damage on your gear your 10 damage number is not going to change any, but your fire attack is going to hit twice as hard (so 200 damage per hit). Any stat with an orange diamond next to it is not included in your damage stat. Basically what I am trying to get at here is your 146k damage stat means jack shit for determining how good your character is. That number is basically nonsense noise when I read it, and it should be for you as well.
Dahbomb mentioned this yesterday, but, the endgame of Diablo 3 is about finding broken item and skill combinations. Since there are no "better stats" on gear (since everything is level 70 and has the same stats) you are going to need to look for these item combinations if you want to move up in difficulties.
That said, from your minimal description it sounds like your gear might be out of whack. Ignoring broken item combinations right now, as that is more of an advanced thing when you actually hit torment difficulty you should make sure you have DPS stats where you can get them. As a brief example (since I don't really want to break down every single piece of gear in insane detail):
Make sure your gloves, rings, and amulet all have your primary stat (str/dex/int), critical hit chance, and critical hit damage. Your amulet should also have elemental damage. Your bracers should have your primary stat, critical hit chance, and elemental damage. Your weapon
needs a socket. This is not a suggestion, a weapon with no socket is worthless, to the point where blizz knows this and 2.1 is adding an item that allows you to put a socket onto a weapon. That socket needs to be an emerald. Every other gem in a weapon is absolute garbage, even a ruby.
D3 is a game centered around critical hits, meaning a fairly high critical hit chance and critical hit damage is required to break into higher difficulties. If you follow those rules above you should be able to do Torment 1 no problem. But somehow If you are following those rules and still having issues it means that your build is a problem and you need to change some things around.
Past that the game gets more advanced, but, what I was describing is more of a starter guide before shit hits the fan.