My Deathknight rotation:
PS-IT - HS - HS - DS - DC ->
DS- HS - HS - HS - HS - Repeat
Abbreviations:
PS - Plague Strike
IT - Icy Touch
HS - Heart Strike
DS - Death Strike
-> Dump
Note: It's important that you keep up your diseases, with either Death Runes or the Unholy/Frost. Your rotation can get a bit off for many reasons, like dodge, misses, movement fights and whatnot.
It's really important that you keep above 25 Runic Power - Death Strike glyph will cap damage on 25 Runic Power, so try not to go below.
Dump Runic power when the runes are refreshing - and dump RP before capping it.
Dancing Rune Weapon
Try to use Hysteria before you use DRW. Also monitor your procs like Unholy Strength from Rune of Fallen Crusader, trinket procs and then use them with these. Nowadays you just need the minimum amount of 60 RP for DRW to last its entire duration of 17s and it's not affected by Runic Power Mastery anymore. Make sure to refresh diseases once you have spawned your DRW to maximize its damage.
There