Match-ups:
Donphan: 60-40 Favorable
The advantage of Donphan is its speed. 1 Energy for 60 Damage as a Stage 1. The advantage of Serperior is that Donphan can´t hit Serperior as hard as it has to. Damage Swap combined with Royal Heal easily takes away 60 damage. If Donphan can´t get the deck down before you have some Serperiors on the field, this deck is definitely in favor. In my opinion Donphan has to tech against Serperior.
Cinccino-Tech Deck: 55-45 Even to Slightly Favorable
Ciccino is (in parts) like Donphan, but it hits for 100 damage, which means it can OHKO Servines. Cinccino is also a bit faster than Donphan. But if Serperior gets the damage lock, it´s going to be hard for Cinccino as well.
Reshiboar: 40-60 Sightly Unfavorable to Unfavorable
This is the worst match-up for Serperiors. You´re still able to win, if you get a Zoroark ready in turn 2, but if you knock out one Reshiram, the next is ready to attack, because of Inferno Fandango. If there wasn´t Zoroark, you would lose this match-up in most of all cases. Your only hopes: 1. Your opponent doesn´t run such a speedy version of Reshiboar; 2. Your opponent has a bad start.
Speed Zekrom: 40-60 Slightly Unfavorable to Unfavorable
If you don´t get donked, there is a chance to beat this deck. You have to get out Zoroark with PlusPower and OHKO a Zekrom. Unlike Reshiboar, Zekrom can´t get the Energy back so easily, which is the advantage of Serperior against this match-up. Until your opponent gets the Energy back, you can set-up, while exerting pressure with Zoroark. However, Zekrom is the number one Donk Deck in the HGSS-on format and you might have lost the game before you even started.
Did you actually test with this deck, or did you pull these numbers out of a hat? Otherwise, good article and analysis; even though I don't think this deck will be viable.