I have no idea how to submit fixes so I'll just paste it here.
This fixes ticks not showing up for warlock channeled spells in bcc.

Modules\Player.lua line 208

--Warlock
[GetSpellInfo(689)] = 5, -- Drain Life
[GetSpellInfo(5138)] = 5, -- Drain Mana
[GetSpellInfo(1120)] = 5, -- Drain Soul
[GetSpellInfo(755)] = 10, -- Health Funnel
[GetSpellInfo(5740)] = 4, -- Rain of Fire
[GetSpellInfo(1949)] = 15, -- Hellfire

Quite remarkable this has gone unnoticed for so long :)