Is absolutely corruption a huge dps loss over siphon life?
There’s some parameters missing from your question.
Depends on the fight, on permanent single target up to 2 permanent targets with occasional add spawns, SL is by far better than AC. Some fights you can abuse AC (Rasta) and tick corruption on Bwonsamdi while upstairs, or tick corruption on Rasta while downstairs. But generally SL is a LOT better