#showtooltip
/castsequence
/cast [mod,alt,@PLAYER] Death and Decay;
/cast [@target,exists] Death Grip
trying cast Death and Decay at my feet then Death Grip(ing) my target in on button push
A number of things, the most important of which is that you can’t combine multiple abilities that are on the GCD into a single press.
D&D has a standard 1.5s GCD and Death Grip has a 0.5s GCD (if you’re ever not sure, look at the Spell Details on Wowhead)
You could do it with a castsequence as 2 presses but you’ll need to change the D&D to @cursor or Death Grip will give you an invalid target error.
#showtooltip
/cast [@cursor] [] Death and Decay, Death Grip