Parsers don't show crit dmg on dots, and if they do, it is just estimated. There is no way to figure out true dps increse as smn since theres a lot of guessing and alot of bugs when it comes to smn. however, I can imagine that, IF dots are critable, the softcap would be around 12-15% critrate, which is easy to get with ilvl90 gear. however, before, you shouldnt bother to get anything else than a hitcapped smn with full dl.

HOWEVER THIS: I have my own theory when it comes to determination and if it proofs to be correct, I will post something here, on reddit, on youtube and live on my stream with a full detailed spreadsheet + explanation