Probably. He was in his early 30s when he played the role. Some quick googling shows that Miyauchi (V3) and Takasugi (Super-1) were around 30, too, but Hosokawa still had a couple years on them. Naturally, he stands out even more when surrounded by all the 20-year-olds that make up the rest of the Heisei Rider roster.

I thought it was cool that Hibiki wasn't a young-gun pretty boy. Nothing against pretty boys at all, I love pretty boys they're the best kinds of boys, but seeing an older dude running around beating up monsters was neat.

It kinda makes more sense too, as much as I like Haruto for example, it's hard to be convinced he is actually the guy in the suit when he looks like an anorexic oriental Justin Bieber.

Yeah, Wizard's kind of got a bit of a noticable build difference than most other riders between human form and rider form.

To be fair it's quite surprising - and poor - how rarely the suit actors and civilian actors match up. Power Rangers has at least some excuse but when the action is made specifically for the show, as it is with the Japanese Originals, it just seems wrong that they can't even match the two halves together.

What is the point if I'm not even convinced that they are in the suit?

Let me explain it for you:

A WIZARD DID IT. :lol

It's a problem for me in PR less because of build differences, but height differences (The blue and pink rangers in civilian form are the same height, but when morphed all of a sudden the pink ranger is a borderline dwarf and the blue ranger just got a growth spurt? What?).

I can tend to look past a character's build if the height stays relatively the same (Which it generally is in Wizard's case).

That's, again, why I like OOO and W so much. They really do a good job of portraying the character in the suit to the point where I have to wonder if that's actually the actor wearing the costume.

How would one go about finding out who plays the riders in the suits, anyway?

You can just google it.

*cough*
http://kamenrider.wikia.com/wiki/Category:Suit_actors