I prefer cast sequences for my DK over click macros. With a cast sequence, you have absolute control over when each ability fires versus a click macro which is better suited to first come first serve type rotations. And I also agree that unless you are playing a DPS dk, you are better off leaving out any rune power abilities as they may lockup your sequence if you do not have enough rune power to use an ability. As a DK tank, you will find that you cannot reliably gauge how much rune power you have due to the nature of random rune strikes. Here is an example of my single target cast sequence:

/castsequence reset=combat/5 icy touch, plague strike, death strike, blood strike, blood strike, death strike, death strike, blood strike, blood strike
/cast rune strike

There is a gap after the blood strikes where I am waiting on runes to refresh before I can do the next death strikes. If I have rune power, I will do death coils here or just wait for the runes to refresh to proceed on with the sequence.

Here is an example of a dual wield dps dk macro where I know for sure that I will have enough rune power to perform each frost strike:

/castsequence reset=7 icy touch, plague strike, blood strike, blood strike,obliterate, frost strike, frost strike, obliterate, obliterate, obliterate, frost strike, frost strike

These are tailor made for specific talent builds and specific glyphs. The duration of your diseases can vary if you have epidemic and other factors affect when you want to cast abilities.