DLC items do count towards your inventory capacity, and can be sold, destroyed or sent to the battle tower chest.

After deleting the DLC, turning off the Xbox, restarting, redownloading the DLC and starting a new game, I get the exact same stats as I described in the 'more questions' topic I linked to above.

sword...: +8 melee damage, +2 strength, 2 charm slots, Fire Curse 6 / Life Leech 4
armour..: +1 ranged armour, 1 charm slot, Magic Protection 1
leggings: +8 ranged armour, 1 charm slot, Magic Damage Aura 2 / Ranged Protection 5


However, in a save at level 23, just before getting the battle tower, the stats are different.

sword...: +2 Vitality, +29 mana, 1 charm slot, Life Leech 4 / Increased Damage 4
armour..: +1 Heightened Reflexes, 1 charm slot, Life Line 2
leggings: +27 Hit Points, +2 Spirit, Retribution Aura 3 / Life Line 6


In my next save after that, at level 31, I no longer had the set (I sold it at some point).


Some time ago I reloaded the same level 23 save above, got the battle tower, completed the first dragon fight, and saved when I was back in the throne room. The Blood Echelon set has different stats here (screenshot 456KB).

sword...: +45 Hit Points, +3 Dexterity, Life Leech 3 / Increased Damage 2
armour..: +5 Mana, Magic Protection 2
leggings: +25 Hit Points, +4 ranged armour, 1 charm slot, Increased Mana 4 / Magic Protection 5


I don't know why the stats would change. I don't recall when I sold the set. Maybe the last Xbox firmware update reset something, and the set got put back in my inventory after I had sold it, so reloading the level 23 save, stats were randomized again???
I downloaded the patch before getting the DLC, so that couldn't have changed anything.

Later I will try re-taking the battle tower, and starting a new game, but waiting until level 2 to open the inventory and check the set....