This post is to talk a little bit about the warp table and how it will effect your army. This post is to also act as a brainstorming session to find ways to make the warp storm work for you.
Warp Calm has no effect on your game, so I will limit discussion in this post on it.
Never Tell Me the Odds
First of all, some parts of the table are just bad, while others are extremely good. A 2-4 will hurt you , while a 10-12 are pretty sweet. As anyone who has played Settlers of Catan knows, that 2-4 and 10-12 are not commonly rolled numbers. They will happen but not every day.
Fateweaver
Fatey is now a support character. His best feature (warlord trait) is that he allows you to manipulate the warp storm table.
You have ~16.66% of rolling a 4 or less on the warpstorm table -- what we define as a 'bad result' Just make it a standard practice to reroll any of those dice. This practice will alter the chances of a 'bad effect' on the warpstorm table from 16.66% to a 2.77% of getting a 4 or less twice in a row.
Secondly he can manipulate the dice results from the warp table itself. You should almost never be rolling a 7 with Fateweaver. Lets say you roll a 1 and a 6. Use Fateweaver's special power to pick up the 1 and reroll it. You have a 83.333% chance of changing a null result to an effective result.
You can do the same thing with a 2 and 5 result or 3 and 4 result. No matter what, there is no chance of you getting a result less than 5, meaning at worst your going to 'null out' again, and are much more likely to get a good result.
The warp storm table is not the 'end all-be all' but its an excellent tool. Fateweaver is the
HQ that lets you exploit it.
Bring the Pain!
So the vast majority of your 'hits' will be 5-9, or wraths. This is a good thing, as they will hit your enemy units causing 'free' damage.
Limiting the Return
The balancing factor of the wraths is they also impact your units. This, however, can be mitigated to not impact your army as badly.
Playing the Right Gods
Of these wraths, Rot and Prince are the most common, meaning that Tzeentch and Khorne friendly models are more likely to be hit than Nurgle and Slaanesh. This means if you go mono-slaanesh your going to be hit less often. However, mono builds have a big drawback in that every one of your units are risking a hit when you roll that result.
Instruments!
Adding an instrument to your army dramatically changes the odds, due to the role of rerolls. Rerolling a 1/6 chance means your units go from being hit 16.67% of the time to 2.77% of the time. Those are workable odds. So the idea is simple. Make sure you have one instrument for each god/pair that your going to be working. If your fielding a slaanesh army, have a unit of bloodletters with an instrument in your army.
Who Cares?
With some builds you just won't care. Lets say your nurgle unit are 15 deckchair plague bearers. Those guys will just sit in area terrain/ruins for the entire game. Dropping one blast on them is not that big of a worry. If that's all you have, I would skip the 10 points for an instrument on horrors.
Placing the Blast
You get to place the blast marker. This means place it on the edge of your unit if you have to hit yourself. This can limit the damage that you do to yourself by increasing the scatter distance. In some cases this does not work, like with a soulgrinder.