Which Hero U think is Better and useful then other one
It all depend on which mode.
1. Rambrad is good in GW and also good as support for Team modes with revive and partial healing and damage reflecting (half of team in same time)
2. Landwalker is good tank in raids and pvp.
3. Occultist is great support hero, which can help your heroes to survive longer, but also remove status effects, and raise attack, not mentioning about healing.
If we are talking about usefulness than in my opinion Occultist would be in first place, Rambard after him, and LW as last. But this is only my opinion.