I was going to level up a party on Ragefire/Lockjaw with the foundation being Warrior + Cleric + Bard + Shaman. The last two slots I wanted to fill with mele dps which I already made two monks for it. For those last two dps slots, if the primary function I want out of them is good sustained dps (benefiting from the bard and shaman later on) is there any reason not to go with two monks or I would a gain a big benefit from swapping a monk out with a different melee instead?
This is pretty close to the group I typically run with. You may want to consider the advantages of having a zerker, rogue or ranger in for one of the monks for headshot/assassinate/decap. You could also have another dps on the cleric account to swap in situationally, there is plenty of content where two healers is overkill. I like to have options depending on what I am doing, and starting with the shaman-bard-warrior base gives a lot of flexibility for the other three slots.
I run the same combination, and I fully agree. The extra attack/hp from the ranger buffs is a nice bonus, and now that Omens is live, Auspice will give a solid boost as well. You can get more dps from having a second monk, or even a berserker, but I think you get more versatility with the ranger (extra offtank, snares, attack + hp buffs, ac buff/DS, headshot) in the long run.
You are never going to properly min/max on a ranger box. Monk/Zerker is the best option followed by Monk/Rog.
I find for 99.9% of what I do, bard tracking is just fine. In what scenarios do you need the extra range provided by the ranger? If it's raid scouting, sure I understand. In normal grouping, though?