Well, Sentinel gives you an extra wolf, Druid is a wolf. Depend on PoV.
But Hybrid Sentinel gives you both the wolf and access to Druid encounter powers as you follow the Hybrid Sentinel rules, not the Essentials Sentinel rules...
Hybrid Sentinel|Shaman even gives you a Spirit Companion, who with the hybrid talent feat can be a wolf
Hmm, that's a good idea, I hadn't thought of that! Hybrid sounds tough though. But that is a genius way of getting around the essentials handicaps...