Your group is multiple classes, which adds flexibility but requires more total abilities to be used for maximum potential. I believe you can do any of the instances with what you have, but if you feel the need to level another toon, it doesn't take too long particularly with the others to boost you.

You have Shackle (Undead), Sheep (Humanoid/Beast), Hex (Humanoid/??), Root (Melee)/Cyclone(Any), and a very good AoE tank that doesn't require a lot of CC's to be effective. That's probably enough CC for starting instances, and the more your team gears the less you need CC's anyway. Basically, if things hit too hard for your tank to handle or the healer cannot keep up with the damage, you add CC. But, once your tank has the defense/armor/health to withstand the burst, and your healer can maintain the steady damage, all CC does is slow down your kill pace. You have a fair amount of AoE - Arcane Explosion/Holy Nova/Consecrate/Hurricane/Shammy AoE (when implemented) with only the Druid requiring non-macroable aiming AoE. If you were to use the druid as heals on AoE's, the mage could Blizzard/Frost Nova. Either way, a lot of AoE power.

The team has good synergy with the mage Scorch glyph for spell crit, Totem of Wrath/Wrath of Air Totem, Druid Earth & Moon, Paladin caster aura. I think you'll be fine with your current team.