Tira is about 6:4. Yun-seong IS 5:5. That's not what I'm talking about.
I'm saying the rest of the characters you quoted as having bad match-ups against Siegfried (Rock, Seong Mi-na, Yoda, etc) have less good match-ups than Siegfried - that is, they have maybe one or two good, or even neutral, match-ups, as opposed to Siegfried's six or seven good/neutral match-ups. You basically said "Siegfried's great because he's better than all the low tiers." That doesn't make Siegfried great, that makes him mid-tier at best - no more, no less.