the macro procs for the first true statement
as written it will only cast deathgrip at your target, btw [@target] is redundant and is the same as []
also [mod:alt] [@focus] means [mod:alt] OR [@focus]. as written shift+R just casts on your target
#showtooltip
/cast [mod:alt,@focus] [] Death Grip
you may find that @mouseover to be more helpful than casting on your focus. you can try this
#showtooltip
/cast [mod:alt,@mouseover,harm,nodead] [mod:alt,@focus,harm,nodead] [] Death Grip