You mean, only Burning Crusade Instances, and even then, specifically the five-man instances.  The Keepers of Time instances in Tanaris have heroic difficult, as well as, I expect, the new five man in 2.4 in Sunwell probably will as well.


As for heroics, they're geared for 70s and were originally intended as a step up to help gear you in preparation for Karazhan and/or Gruul/Mags; the gear that drops reflects this, as does the difficulty, generally, anyway.

It is entirely possible to do a heroic without epics, or with lots of blues and greens.  I started running them when my only epics were the crafted PMC set, and everything else was blue/green; they were pretty hard then.  Of course, in T4, they're easy, and in T5 they're a joke...

In terms of progression, if you've ran most of the instances on normal without much issue, and completed most of the important questlines, you should have plenty of gear to pull it off

The odd thing about heroics is that it isn't usually the boss fights that are THAT much harder (usually just a bit longer and requiring a slightly different strategy).  It's the trash, lol.  The first time you get hit for 9k from one of a pair of sentries just inside the instance (which are immune to cc, so have to be tanked) it is a shocking gear check, especially for tanks.

I started healing heroics right after dinging 70 on both my resto druid and priest - graced by having well geared guildies to run with.  But neither of my healers was particularly undergeared and both were highly enchanted/glyphed/inscribed.  Heroics benefit the newly 70 the most, as that is when you need gear/badges.