to track CP (combo points) on my druid, i use Hear Kitty. It'll play a sound every time i get a new CP, the sounds are easy to identify and 'count' ur points, and when you spend/lose the CP it'll play a sound to notify it. i think it's a great addon to track CP without putting some more stuff on ur UI.

Have you tried ShockAndAwe? I'm not sure how Enhancement Shamans make it through their priority list without it.

ShockAndAwe is awesome for enhancement shammys.
Again, since NeedToKnow is more of a timer based bar addon, Maelstrom stacks don't really fit the bill. That's where PowerAuras can help if you don't like ShockAndAwe.
You can set it to show certain auras at a certain stack count of buffs. Set one aura to 4 stack and another to 5 stack so you know instantly when you can use it. You can even go creative with changing colors based on stack or the aura building up to complete a circle on full 5 stack.

Certain things you're just going to really need a class-specific add-on for. If you can see the third screenshot up there, that's Scorchio2 for mages. (Since that's my UI in the shot. ;) )
I use that for class specific timers that I don't need tracked via NTK.

There was actually an excellent Youtube video done by an Enhancement shaman showing how he counts Maelstrom through Power Auras, and now I do something quite similar on my Mage to count "AB points".

Make 5 different auras, all for Maelstrom, and change the stack counter for each of them so that they will stay when the stacks grow, but only appear at a certain amounts, i.e.

I don't have an enhancements shaman to test with, but I would think Maelstrom Weapon would just work as a buff on the player, and it will show the number of stacks next to the name like any other buff.