As I said, a RDM & a WHM in your party, this provides 2 healers, also it allows for the RDM to Phalanx everyone, helping with damage mitigation, while also giving Refresh II to your WHM, allowing them to have more MP supply. Now days there is alot of refresh gear for jobs, so that can help as well so long as they are in that gear when not healing. As for your list of things to take into account, don't have everyone on at once if it becomes a problem with hate, fast cast shouldn't be needed since your melees are doing no casting, your RDM can do things fast still. MDB I will give you, but still, gear can do it. Enspells and spikes are not much damage, in fact since your using a WAR as an example, your WAR should easily outdo a RDM right? So thats nothing to matter, unless you meant spike enfeebles, which your RDM can easily provide via casting.