I provided a mathematical proof. I added both damage procs to the 'inferior' bow and added combat archery to both bows (original calc was lvl 20 for ship-siege, the one you wanted is lvl 21 for shadowstrike). Your simple example is only adding to one and has 0 multiplication (what happened to crit multi/range and ranged power?)
Any future reader is free to double check the math performed and suggest corrections or point out flaws. I listened to your concern of 5d6 (vs the 4d6 I originally looked at) as well as the Disintegration Proc and created a new post to run the numbers for you. I left the original post as lvl 20 as it is fundamentally different than a lvl 21 calculation with Combat Archery. If there is a problem, then please prove your stance running actual numbers (in any format that can be reviewed for mistakes as I have attempted). Including my calculations and not just the end result is the exact opposite of false or misleading but an attempt to show how I arrived at the conclusion.
Looking into your own math I would like to point out my own concern.
I would like to point out the flaw of not considering ranged power or even damage bonuses. Simply adding procs will provide the result you so wish and I acknowledged that here. I did not skip the step. I had yet to reach that point in my calculations which I addressed shortly after in the exact same post, grouping everything together into a singular step makes it harder to follow what happened at each step. After considering the damage procs I admitted that it brought the other bows ahead of Thornlord, I then continued further to include the other factors. The numbers you are quoting from my post clearly stated that they are the base bow damage numbers and do not include additional crit threat/crit multi/damage bonuses/ranged power or even the procs you are so focused on. I attempted to include all of this to show that the damage would then go on to favor the Thornlord to make up as well as surpass the procs seeing as the procs do not scale with these other considerations. I believe these considerations should be used when talking about a lvl 20-21 build that will almost certainly have them in some amount.
Please stop quoting the very base numbers from the start of my calculations saying that I do not consider something when I clearly addressed it later.