The symbology in Collector is more simple than in the webmap. Many times I have done a great symbology in a webmap and in Collector it does´nt work. When working with collector - keep it simple.
If you are not working offline you could have the same layer twice in the map with different symbology or have the layer and a view of the layer in the same map. It could work offline if you are not editing the layer - but if you want to edit the layer offline you will encounter several errors.
Esri will release a new version of Collector with based on a more modern runtime version and that may solve the problem above.