I'd advice that you try all heroics. Even the ones that are listed as difficult. You might not be able to clear them, but you'll still be able to beat some of the bosses and get some good gear upgrades and badges from them. For instance, you could try to kill the first two bosses in UP after you've cleared UK. It only takes about 20 minutes to kill them and since you're in the area anyway...


Just noticed something... slap some sta armor patches on your gear to get 1-2k hp extra..
18k = dead tank
20k = no room for mistakes
24k = it's going to be a rough ride

And if necessary put them on your other chars as well, it will make aoe heavy encounters like the colossus a bit easier.