Try it in a duel a few times.
If it works for you, it's fine. It's nice though that you're taking advantage of multiple forms, just keep in mind that you can over do switching forms, thus dragging out a fight longer then it probably needs to be - specially in arena. The more time it takes you to kill someone, the more of a chance it is for you to be ganked by his team mates, but again, whatever works for you and gets you the kill fastest without dying.
You're probably not going to use the same combo for each player despite their classes. It's up to you to judge how much damage you're taking and how much damage you're outputting to decide if you need to take advantage of your other forms. Some players you'll be able to one combo in wolf, some you'll have amazing RNG luck with your stun hammer and just stun lock him to death, others you're gonna need to put in a bit more effort. Judging what you need to do for a situation is just going to come with experience.
After a few arena matches, you'll just know by their IGN who you can farm in just wolf with no problem and who is going to force you to form switch. Remember though, being able to own someone in a duel isn't going to always mean you're going to do the same in arena to the same person. A lot of factors change in arena, specially for Sage.