What a unique idea for a hero. I never would have imagined a frog as a hero in the series, but, knowing Ironhide, it's entirely possible.
His passive trait is pretty extreme!
It takes an entire skill slot for Kahz to deal quadruple true damage with his attacks, and while this has half the chance to occur and deals double rather than quadruple damage, the 2-second stun evens it out, making the critical hit mechanic a very powerful innate trait.
Frog's Tongue Cut raises a few questions for me. It deals 6 damage over time, right? But... over what time? How long does it take to pull in enemies? Nonetheless, I like how heavy-hitting this attack is. I feel like lots of high-damage skills likes Grievous Bites or Mighty just aren't that impressive, so this skill, especially for the weak defensive stats of this hero, is very satisfying.
Frog's Skill essentially matches the innate trait of the hero to that of Kahz' Blood Axe passive. It's just stronger now! I like the risk of sending this very fragile hero into melee to attempt to deal powerful critical damage, and with a stun chance to allow him to fight for a bit without being damaged back, given that there aren't other enemies with ranged attacks nearby.
What the heck is Frog, No Toad!?!? This such an extreme skill, taking away control from the player for 15 whole seconds!?! It's a really cool idea to make a berserker-type hero, but it seems like it's thrown in without really realizing what it entails. An entire hero could be made around this idea, because it really means a lot to have the hero become independent, especially for so long. Even Vez'nan's soul absorption skill, which only leaves him in an animation for about a second, can be fatal. 15 seconds in this game, especially in Origins and even moreso for a frail hero such as this one, is way too much without anything additional to make it work. It's still a cool idea, though, just in need of lots of improvements, or to be replaced and saved for another time where it can be used better.
"I'm Just a Frog."
The name goes well with the previoue skill, "Frog, No Toad."
How is the 15% of enemies chosen? What if there's only 1 enemy? Even if there are 3 enemies, 15% of that is 0.45, so it doesn't even round up to 1 enemy. Also, if they don't attack him, does that mean he can't go into melee combat with them? It's a cool skill, though, since I can see this combining with his berserker rage and allowing him to attack enemies with less risk of being damaged, though the low chance and long duration result in not being that helpful from what I visualize, since he will still take an average of 85% of damage, which can still easily kill him in those 10 seconds, especially during the 15 seconds out of the player's control.
I like the hero spell. It's not very intense or dramatic like some are, but it has a good purpose: distracting enemy fire. Again, this could go well with Fron, No Toad, as it keeps him safe, but it unfortunately also makes I'm Just a Frog useless, since 100% of enemies are going to ignore him for the fish, making the 15% chance to ignore him have no impact. It has good utility, though, so maybe the other power can be changed a bit to improve the way all of his powers come together.
The way I see this hero as a whole, he's got very nicely-chosen numbers for his stats and ability damage. The only thing I dislike is how the abilities all come together and get in the way of each other. Some skills in heroes work really well together; Lynn uses a weakening AOE that has the same cooldown as her Hexfury attack, and it increases the damage of that skill as well. Xyzz will use a skill to keep himself safe from enemies to a small extent, then go out of control from the player, has a base attack resulting in stunning enemies with critical hits to avoid damage, with a hero spell that distracts enemies so they don't attack him. They all serve the same purpose, but rather than make him really good at fulfilling that role, they don't make an impact if another one is already in effect, so the skills get wasted. I hope you understand what I mean by all of this. I really like the idea od this glass cannon, dealing really good damage and using stuns to be able to sneak into battle without suffering damage in retalition, but the doesn't come to fruition as much as it could, and gets contradicted by not being able to control him for such a long time, grealy risking the chance of death unless you use the hero spell, which nullifies his stun passive and the effects of I'm Just a Frog.