I would have the Leapfrogger’s death rattle to only pass to another beast without death rattle. Problem fixed and still playable. 
Without the deathrattle it would be a terrible card that just gives a 1 time bonus of +1+1 that would make it worse than any other t2 beast so unless you plan on keeping 4 T2 cards in your deck for a long time there would never be any reason to buy it.
The hummingbird alone gives a constant +2 attack bonus to all beasts even summoned ones.
Why would you want a 1 time +1+1 bonus that only applies to 1 creature 1 time instead of the bird that gives +2 attack to all the beasts while it is alive?
Then you have the rooster and silver goose which is a great combo early game and all 3 of these cards could stay active in the lineup for a longer time much better than the leapfrog without a deathrattle would.
Also the card is called leapfrog because that is what it does, leaps from beast to beast.
They would have to rename it The +1+1 bonus toad.
No.
Yeah I’m super tired of the frogs they need to go. Maybe it’s just me but I don’t understand how a frog jumps and then they gain 40 to 60 health and damage
IF you have a normal Rivendare and a Golden frog, and the Rivendare always stays alive, and by some weird luck every frog always leapt to the best target, THEN after n hops you would have 2^n in stats. That’s exponential scaling. In practice, the hops aren’t perfect, they’re random, but the power of that kind of scaling is still huge if the x in x^n is between 1 and 2.
The best frogger comps maximize Mamasaber triggers precisely because it increases the n in the formula while protecting Baron with Taunts. Leapfrog provides the base and Baron scales the x, but it’s summoning a lot of Beasts in combat that scales the n.