Yes, it's true. Suicune is the only legendary I would have in my party. Every time I catch a legendary, it is sent to the box. If it is Suicune, maybe - MAYBE - it is moved to my team.
Suicune, in my oppinion, is one of the less over rated pokemon, seeing as you have to train it relatively alot to get the best moves and stats out of it
Your are right they'res no fun in training a pokemon thats already high leveled. It's more fun training normal pokemon =) The only legendar I would have in my team is an Articuno im just like you.