are you using it for the evade chance and overcapped dci in tiger form or to get a greater chance of not being revealed when stealthing with shadow active? then yes, it is worth going lvl 3.
If you only use it so you can use tiger form for mounted speed at 90 ninjitsu, then no.
Comments
I'd pretty much say yes it is.
"To get a greater chance of not being revealed when stealthing with shadow active?" - for that reason alone if you stealth.
As a rule, I find the jump from level 2 to level 3 Mastery noticeable in terms of ability gains.
Added to this, Ninja primer 3 drops like water, it hardly costs anything to buy and add.