I mean no offense, but it seems you do not have a solid grasp of DDO's mechanics yet.
Rogue gives you no extra ability to dual wield.
Ranger has no "elemental" spells.
A pure cleric is far far more effective than one who takes levels of rogue or ranger. Staying pure Cleric is not only simpler, its more powerful!
As a note: You do not need to dual wield. Your damage comes from spells and the crazy raging barbarian you are singlehandedly keeping alive. You do not need range. Your spells are you range (Though the only good offensive ones come in later in the game). You do not need elemental spells. You can command, bladebarrier, destruct, banish, and implode. You are a walking death machine who just *looks* like a healer.
As has been said before, unless you plan it from the very beginning and know exactly how and why you are doing it, don't multiclass. Its too easy to ruin your character's effectiveness without hitting the goals you want.