Hell to hard? Blaming Blizzard for bad tuning?
This is clearly a player-related issue.
1. Go to the menu (the one before joining a game)press "Auction House"
2. Filter out items on slot, lvl, stats and price.
3. Buy the item that seems to be best possible for you.
4. PROFIT!!
Now with higher health, damage and damage reduction (armor, resistance) you will survive longer, and kill faster.
If you already have done this, start looking for other builds.
Builds for Hell/Inferno, you should have atleast one defensive ability (not counting Archon due to situational uptime + cooldown)
Explosive Blast may have high damage, but towards the end of Hell, and whole Inferno, it becomes less useful due to being most effective when surrounded by enemies, and you dont want that to happen in Inferno, because then you are dead no matter what.
You don't have any Slowing ability, so you cant kite mobs that will 1-shot you.
You also don't have any Armor spell, Energy Armor adds more to survival, and with any of the last 2 runes to it, your survival will get even higher.
This is just a handful of tips, i bet there are way more to come with.