DK in my group question

Hi all,
so I have a Dk sitting at 80 which I originally tried to use as a tank for my first multiboxing group. My question is, should I retry him as a tank now that my dps are pretty well geared or change his spec and move him to an account as a dps?
As a tank it would mean either use my pally as a healer (he has a lot of high level holy plate from drops in the ICC dungeons and was originally holy solo) which loses all my AoE heals and so would limit what dungeons I could box in or move him to another account where I could keep my druid as the healer.
So rarely playing my DK, If I move him onto an account as Unholy for a dps spot, will he be doing a lot of melee damage or does this spec do more casting? If melee then I would need IWT in his keymaps in ISBoxer?
Currently just seems a waste having an 80 sitting in blues :P

So I have been thinking about the above DK group and I may move him so that the group would consist of pally (tank), druid(heals) and DK plus 2 BM hunters. I am thinking this might be a decent setup.
Any thoughts?

Your DPS will be hard to manage, you want more 1 key spam. Mage or locks. If you do go with the 2 hunters, make them MM and forget the pets. I mean, you have pets and they just run around melee'ing mobs but they are not a huge part of your DPS. MM/SV are both higher DPS, and easier to box with. This is from a long time BM huntard.
DKs roll DPS but there is not a real good way to 1 key spam them either, have to make sure that spell a then spell b before spell c.

So then maybe I should go back to trying to tank with the DK., I know it was hard when I started out first using him but I am thinking thinks should be a little easier now that I am more familiar with strategies etc for running dungeons :)

It doesn't hurt to experiment, see how things are now that you know where to position toons and such.

The DK is probably the worst tank in the game, from a boxing standpoint, although warriors have a bunch of proc type things which makes them hard to play boxed optimally too.

However, the DK brings you the 13% spell power buff to a caster group, or significant melee buffs like 20% haste from deep frost. A Pally gets you an aura and a blessing, which is decent but from the standpoint of increasing the power of the rest of the group, the DK is probably peerless.

Thanks for the insight, I really jsut feel the DK is currently wasted and sitting in blues. He has 245 defense but a little low in health at 20k.
I think I might be able to pull of some heroics with him tanking to just get some badges to gear him. You are correct in the statement that I probably should just experiment :)

Also, depending on where the other tanks are on your accounts..
You could possibly run him as DPS, even if its not optimal.

But with the rest of your group, and a geared tank + healer, you could run a bunch of heroics relatively quickly, and then buy badge gear for the DK.. which would make tanking a lot easier with some gearing.