You have to balance between ease and power.
The more things you manually click or cast the higher the dps or more threat you will deal.
The more things which are a castsequence, and the easier your play will be.

Your tools for semi-automation are "Castrandom" and "Castsequence".
You're still going to get one action per one keystroke.

Ideally, you'd like to go Flame Shock, Lava Burst, Filler Spells, Lava Burst, restart sequence.
Because Lava Burst will automatically crit after a Flame Shock and its our top dps spell.
Elemental has a talent which reduces mana cost for offensive spells after a crit.
Ideally cast your more expensive Chain Lightning after the Lava Burst.

A cast sequence will occasionally have a spell be resisted.
A cast random will sometime cast Lava Burst before Flame Shock, which removes the auto critical hit.

For maximum shaman dps, you'll want to be able to manually cast these four spells.
For ease of play, you'll want to be able to mash one button and not think about it.
I've personally put these four spells on four keybinds, so I can push them in the order I want.
I've put my pally tanking macro onto all four keybinds, so no matter how I dps the pally clicks the tank macro.
You could go the reverse, and have the shammy dps macro on a few keybinds and click pally abilities as you want them.
Or optionally put them both on macro's and have a very easy time just mashing one button.

Anyway, shammy spells you'll want in your sequence/random macro or to click:
Lightning Bolt, Chain Lightning, Flame Shock, Lava Burst.

Paladin spells you'll want in your sequence/random macro, or to click:
Hammer of the Righteous, Shield of the Righteous, Judgement of Wisdom (or Light), Consecrate (unless you manually cast it), Holy Shield, Divine Plea (unless you manually control this).
There are threads for Paladin tank macro's. I'm toying around with one I found.

/castrandom Holy Shield,
/castrandom x, y, z.

There is a comma after the Holy Shield. This means half the time the macro clicks Holy Shield and half the time it clicks the null.
When the null is clicked, nothing happens, which gives the second castrandom a chance to kick in.
When it does, it randomly clicks one of the abilities.
If you want a 1/3 chance of Holy Shield, make it read: /castrandom Holy Shield,,

The search feature will show you what has worked for others.
You'll end up with a system that works for you.
Share anything you find to work well or that is cool or innovative, others will appreciate it.