nah I like death dealer in the front row, it gives a challenge to chapter 10 (think of using death dealer in chapter 10 as a sort of nightmare mode for the campaign, any of the missions actually)
plus its an artist decision which was explained when they reintroduced the new stats on the 3 heralds
its difficult but not impossible to beat mission 10 with death dealer, demons was my first faction I completed the campaign with, just better your strategy for chapter 10, make like a 20 card deck with some units that have less HP than death dealer, you can also use 4 death dealers if you have them, that way as long as one survives you still win.
another thing, use as little back row units as possible, gwydion succubus and nagle mage are my only back row units I ever use