Incorrect. Full sized Eurex DAX futures trade in 0.5 ticks. It is the smaller mini dax futures which trades in 1pt ticks.
The CME clearing cost is not 1/10. If you take the ES, the CME fee is 1.18, for MES it's 20 cents. If it was 1/10, it would be 11.8 cents. But, it's almost double. You also need to add routing that at times is just as expensive as the exchange. There is a level that is good for MES Micro Emini SP, but at a certain quantity, it makes sense to trade the Minis (opinion).
OP, don't blame the specs of the contract for your DOM woes. BLAME THE DEVELOPERS of the DOM you're using for not allowing you to change the granularity of each step in the price ladder. Just because they represent each step as a price tick doesn't mean they couldn't represent it as 2, 5 or 10 ticks or vary parts of the ladder with different granularity levels, and alter them in real-time with simple keystroke combinations. Oh wait, I should patent that and give it away before TT files another obvious observation with the PTO and stops innovation for another 20 years.
Although people have been suggesting using software to merge depth levels. It is worth pointing out that will not give exactly the same effect as widening the spread in the contract spec. When the spread in the contract spec is widened it encourages even more orders at each level. If the NQ tick was doubled to 0.5 i would expect to see even more than a doubling of depth at each level. In general, narrower spreads encourage use of market orders (you don't lose so much in paying the spread) And wider spreads encourage more use of limit orders (to avoid paying the spread). A wider spread will also encourage more market making activity, adding even more depth to the book.