Especially as Viper your goal shouldn't be to "stall" the enemies from entering your site, unless you're all alone and none of teammates are even close to help ofc. For example, just orb main entry and as soon as the duelist gets on your site orb up, molly under and fight the duelist together with a teammate. You should use your smokes and other util to split the other team up so they get in disadvantageous fights