Cool list kd, terrakion should definitely be on there though imo. Terra has been the standard for physical attackers since it was released, the posterboy of power creep. Terra began to define 108 as the benchmark for truly fast sweepers in the same way that salamence in dpp meant you needed something with at least base 100. terra has been a huge factor in the dominance of offense > stall, in sand's continuing presence, it was the first common OU mon with sets like double dance, rock gem, even subsalac's popularization has been largely due to terra.
IMO reuniclus is the least deserving on that list. What you say about it is true, but my issue with it is that reuniclus was so ridiculously hyped that we had a hard time figuring out whether or not it really lived up to its reputation. It's true that it did demolish stall, but so much does that this gen, i dont know if thats really enough to keep it there.
Other mons: personally, i dont think latios should be that high, sure it's threatening but it never had the impact of stuff like dnite (another dragon--on the list). Exca should be wayyyy higher--come on, it WAS the meta for a while. I'd put it right after landy honestly. Venusaur shouldn't be that high, I totally get your argument about it being venu rather than tales that "makes" sun, but as you said--sun hasn't been that big of a deal. More like #10 or even higher imo, I could see it just barely making the cut. Dnite should be #3, top 2 are obv and right. Duggy is good, I totally agree with it being on there--it defined sun as much as venu imo (which is why it should be as high as venu) while partnering fantastically with mons like gene and torny-t (which is why it should be higher than venu). Rotom-w so deserves to be on the list, as you said it WAS volturn. It also took on a whole new role as an all-purpose SpD mon, checking torny, landy, rain abusers, etc. A great example of how balance has flourished this gen.
Tl;dr: my order would be something like:
1. Toed
2. Ferro
3. Dnite
4. Landy
5. Exca
6. Jelli
7. Volc
8. Duggy
9. Rotom-w
10. Terrakion
11. Venu
12. Not sure what would go here. Breloom is one option, it totally shook up the meta--spore + super-powerful priority with good typing was huge. Latios mebbe. I don't really think any of the "insta-ubers" really should count--yeah they were broken, so the meta revolved around them for a while but...they didnt really do anything new. Deo-s was replaced by deo-d is being replaced by custap leads and what-not. Gene was strong, but was just another very powerful sweeper with good coverage really, which isn't new at all by now. Xatu or tenta are both possible, as they sorta defined playstyles (sun offense and rain stall, respectively), much as rotom-w defined volturn.