First advice is to follow NSX-T reference design guide. We see no mention there regarding using vsphere HA to failover to another host.
When designing for T0, you have to take into account physical topology and where are your upstream routers, so you are careful not to lose connectivity in case of a physical switch failure. In the case of Active-Active it is always best to have active edges on all physical hosts you have, each with at least an uplink. This way you have full control of traffic. Having edges move around is not good.
Thanks. very helpful...