Berserker snares and stacking...

I was playing w/ my lil necro the other night and duo'd up with a Berserker in Kurns. We were movin about killin stuff and I noticed that my 'Creeping Crud' or whatever the dot/snare is at lvl 16 was not hitting, even on light blues. I know it is resisted fairly often, but it looks like it just won't stack w/ the zerker snare. Has anyone else found this to be the case? Are all snares like that? If that is the case, how long does a Berserker snare last? It would suck if a berserker couldn't use their class abilities because some other class with a longer/more reliable snare was unable to use such a spell. /c: Whats the community stance on that?