MY personal favorite double bless nation/theme is ... wait for it.
Jotun Woodsmen with Death 9, Nature 9.
The trick is being able to get up that high without crippling your research. But I've found it to be very effective.
But when using that particular blessing combination the Woodsmen are particularly nasty, long Lasting and have a good survival rate. Especially if you include them in normal squads of Giant Spear Huskarl.
And you feel that the Death-9 effects are better than the Water-9 for these? (A problem with Nature-9/Water-9, of course, is Jotun doesn't get starting gem sites with both Nature and Water together.) I presume you play Iron Woods or Utgard since they both have Nature + Death starting gem sites?
Depending on what you are trying to do. I'd stick with 2 blessings. I don't know exactly how you're playing now so I couldn't comment . Air 4 will give you 20 Air Shield while Death 4 will give you Lesser Fear -1. It's all in how you want and if you want to pour everything you have into blessings
I use Utgard. I prefer their mages overall. And depending on what pretender you use (I prefer the Master Lich) it can be modified.
The important thing to remember is to take Order 3, or you won't be able to build the required numbers of Jotun to survive. Also with Utgard you can make Nature items, with the kind of scales you are choosing, being able to make extra supply items is vital as well as having some leaders who can command undead. Also it's nice to have a Norna around to stop some of those nasty misfortune events.