I'm jumping in a little late to the discussion, but wanted to give some details of how I geared up. I have a mixed team, and started solo heroics using paladin tank, mage/warlock/shaman DPS, and dedicated holy priest healer. Gearing focus was tank and healer; DPS got little attention unless opportunities and gear presented itself.

I used as much crafted gear as I could: engineer tanking goggles and titansteel shield/boots as well as crafted blues for the other remaining slots if I could make it on the tank, and titansteel guardians for the healer and shaman (spellpower daggers did not exist yet, but used Kirin Tor tabards until I could buy their rep dagger) as well as any blue tailoring/leatherworking gear that I could to boost the healer first and DPS second. I had my own Blacksmith, Tailor(x3), and Leatherworker. I didn't have to buy or trade for any gear before starting heroics.

I was actually doing heroics with only about 527 defense and 22k hps to start, since that was the best I had or could make at the time and didn't want to wait any longer to try or spend any money on the AH. I started just doing 2/3 of H UK (skip Prince Keleseth), 2/4 or 3/4 of H DTK (skip Novos, and usually King Dred), and found all of H HoL easy enough for me (having a great holy priest was key for me for Ionar). I would just keep this easy rotation up each day until I had more epic drops and emblems to buy better gear with before starting to try harder stuff. Luckily, Prince Keleseth in H UK dropped his defense sword on my first solo kill to help boost my defense a little more to the cap, but never bothered with him for a while afterwards to avoid any likely wipes. I probably could have added at least 3/5 or 4/5 of H Gundrak to the list (not do Gal'darah), but just didn't think about trying it right away.

My priest would definitely get a workout at times. Sure, I would get hit by an occassional crit by not being capped, but it rarely resulted in a wipe so long as I tried to keep him close to full hps. Wipes did happen though, but at least I proved that you don't need any min defense or min hps to start heroics. Just do what is within your ability, and then move to more difficult fights as you gear up. I'll have new warrior and DK tanks in a few weeks, so I'll be going through the tank gear grind all over again, just easier since my priest outgears heroics now.