Yep. If I'm lucky, I'll run into one, MAYBE two people when I'm in there practicing tweaks to a deck. I understand how the Iczers lvl. 9 < x must feel-it's quite frustrating. Not too many people are interested in "practicing". Quite a few of people I play in the 1-9 arena have really bad records (3 losses for every win or something ridiculous like that), so I'm confused as to why it's infrequently used.
Cause even losses give you experience toward leveling up and leveling up gives you new cards. Also even if your winning rarely if those wins come during treasure battles your getting new cards, no treasure battles to be had in the training room.
At least that would be my guess. Another reason is as you said, there's already not many people there so its hard to find opponents and you don't really know the level of opponents you might face, the best training for your decks comes against top opponents. Record and rating currently don't count for much of anything so your not really risking much by testing decks in the experience earning rooms where you're likely to find strong opponents. Now during a tournament I suspect people won't be using decks there testing but time tested ones but that's a different thing all together.
The bunnies of Lavato have special abilities, like 'Action Skill: Make Carrot Disappear.'