I have been searching around but never seen any post of this bug so im just gonna post it here and hopefully its not a re-post. Now I only tested this on WoWbeez, idk about other servers.
Step 1: Reset or have a dual spec for your Deathknight (This bug only works for DKs)
Step 2: In your Frost Spec, randomly spec for talents till u have enough to fully spec for Improved Frost Presence - Spell - World of Warcraft (You dont need to use all ur talent points)
Step 3: Now after when ur speced for Improved Frost Presence, Change ur DK's current aura to anything else then change it back to the pervious aura. You can see that ur DKs hp has increased.
Step 4: Reset ur talents and repeat steps 1-3 as many times as u want if u want alot of HP.
Now having a lot of HP will give u alot of benefits since your a DK. Rune Tap + Vampiric Blood
Warning! YOUR HP RESETS WHEN U RELOG AND U DO HAVE A RISK OF GETTING BANNED FOR 24 HOURS!
Thanks for reading! Its my first time posting something so hopefully its easy to follow and not a repost.Feel free to leave a comment or questions about this bug.