So probability is not the only thing that matters.
Sorry, but your wrong. Probability is all that matters, and regardless what you think or see in the short term does not matter, so your point is not valid. Regardless of whether your solo or pool mining, the def fee wont change hard math. Over time, If you solo mine 100 blocks, 1 block will be missed due to the dev fee on average. If your on the pool your hashrate will be shown 1% less on average.
In the theory it is the only thing that matters but I think there are other things to consider aside from theory.
Let's think about a possible scenario: I mine solo with my 300 mh/s and I should hit one block every 1.5 days. If 1.5 days pass and I didn't hit a block, then I can say I missed a block. This can be due to dev time or just to bad luck, let's say it is due to dev time. Then I need to find a block "within time" the next 99, on average. This means that, if everything goes on average, after 150 days my figures will be correct. What if, by chance, I miss 2 blocks due to dev fee? Then I need luckier times or I will go to 300 days to even out.
When the hashrate is so little as mine, it is possible that you need a lot of time for your figures to even out if you had bad luck. And POW is not forever. Is this a correct thought?
If it is not a wrong thought, then there is a hashrate threshold below which it is dangerous to solo mine with CDM because you risk to not even out in case of bad luck. And then for the real mining, not the theory, probability is not only thing to take into account. Please I insist, I am not a math guy, correct me.