Sejuani's slow effect stacks with Randuin's Omen active?

Since Riot made it so that slowing effects don't stack does that mean Sejuani's slowing effects don't stack with Randuin's Omen active effect? I've been building Randuin's Omen with Frozen Heart on sejuani since it is recommended (because of 30% decrease to enemy Attack Speed) but now after reading patch 5.13 is it still viable? This question also takes consideration of item's slowing effects and champion slowing effects stacking. If the slow effect does not stack what would be a viable replacement for Raduin's Omen for Sejuani if any? I've also built Deadman's Plate on Sejuani before but it also slows targets so I have the same problem. ( Is Strak's gage anygood on Sejuani even though she is mostly ap based?)

Sejuani's Slow Effect: 50 / 55 / 60 / 65 / 70% slow for 1.5 sec Randuin's Omen: 35% 4 sec Deadman's Plate: 75% 1 sec

P.S I usually follow this guy's build(Link Up above)