He's a boss in 4th edition. One who is clearly taking on the party with no backup/support.
I see no reason to believe he's following the same rules as a player character, or to assume he has class levels. I would be shocked if he's not designed as a Paragon tier solo encounter. While I am a bit hazy on the rules (I haven't touched 4e in literally at least 7 years), I know the HP there tends to be around 5x higher than a normal monster of that level. I would guess 500hp as a fair estimate to start from. If anyone feels like digging out a 4e monster manual, look for a level 15 Control Solo, as that's roughly where I peg Dire (Though he may be closer to 11).