Warlock (demo) guide to tendon damage:
Step 1: Unglyph meta glyph for corruption glyph and spec incin spec. Use moonwell chalice
Step 2: Make sure you always have a felguard out before the tendon comes up, all tendons.
Step 3: After the first tendon make sure you are incin / sb as much as possible to get your meta cd reset before the next tendon
Step 4: immolate / corruption as many targets while the amalg is blowing up maybe even some before it's dead. This way you get molten core and shadow trance procs for the tendon
Step 5: once the amalg finishes casting it's explosion pop moonwell and run next to where the tendon will be showing up then pop meta /demon soul before it shows up.
Step 6a (optional): cast incinerate to get 5% crit up for the raid. After the cast is successful and you don't see CoE up, cast that as well.
/tar boss2
/tar boss3
/cast Incinerate
Step 6b: while you are casting the incinerate have your pet use felstorm
Step 7abcdefg: Cast Soulburn / Immolate / Bane of Doom / Immolation Aura / Corruption / Shadow Flame / Hand of Gul'dan
Felstorm will have finished doing it's thing after this
Step 8: cast summon felhunter (wait .5second before telling it to attack so it's shadowbite scales after being summoned) then tell it to attack the tendon
Step 9: spam incin, use shadow trance procs, and use hand again.
Step 10: if the tendon has less than 1.5~1.7 seconds left spam fel flame
When the tendon goes away go back to step 2