Idk about standard but it definitely is in wild. Besides reckless experiment being busted with you could also get a third mechwarper (faceless, simulacrum, cube, brann + Zola, Floop, there's a whole bunch of ways to do this) and it becomes a 0 mana echo card. Either OTK your opponent if a mech sticks or just play literally infinite stats on board for your opponent to deal with.
Nice to see the dev team still give 0 shits about wild balance.
In Sn1p-Sn4p's case the Reckless Experimenter takes the role of our Mechwarper and the legendary mech has the Glinda's effect, so the TTK combo will work as people have suggested it. Though imho Coppertail Imposter won't be the only mech in that deck, because it can be easily answered by a lot of board clears. The priest players have to add more mechs in their list for better consistency, Dead Ringer will fetch Sn1p-Sn4p and a new competitive archtype will be born.
The turn 5 OTK will be extremely difficult to pull off.
First you have to have a mech in play. And yes, there are ways to kill stralth minions as well.
Second, you have to actually find the cards: the 5 mana dude and the legendary and is going to be very lucky if you can find a combination of 2 very specific cards (one of which you can only put once in the deck) by turn 5.
Last but not least, the whole combo is easily prevented by your opponent having even a single taunt.
Will we see otk on turn 5 on youtube videos ? Absolutely yes, those small chances actually happen when tried enough times.
But will this actually be a problem in general ? Absolutely no, the possibility of this combo happening is so small that it might not even be worth changing your deck to fit it in.
Card is completely fine for a legendary and nothing to worry about.