It's a lot of hoops to jump through for nothing but an under-costed minion.That's good enough for Edwin VanCleef and some of the giants, so maybe. I don't like this card's chances at the competitive level, though.
The thing is, pretty much every Grimy Goon card is a battlecry. So, basically this gains extra buffs from the Grimy Goons cards.
But is it worth it? Probably not, considering other minions have better base stats... you would have to play this really late in the game for it to be good enough, but would you really want a well-stated 3-drop at that point?
A self-buffing Grimy Goon in a lot of ways. Most hand buff effects are from battlecry minions, most value drops are battlecry minions, and most tech cards are battlecry minions. You might even consider that it's like have Brann Bronzebeard in play when you drop something like Grimestreet Smuggler. It could end up being something you dump out at 8/8 or greater stats alongside a flood of buffed minions, but at that point you might as well just take another battlecry minion over this instead. Growing in hand has been around since Bolvar Fordragon, but I think there's finally some potential for that kind of card in a Grimy Goons deck.
Comparing to Bolvar isn't a fair criticism. Bolvar didn't gain much value until he's at least a 5/7, 6/7, or 7/7. Back in those days you still had literally every deck running 1 or 2 silence cards plus Big Game Hunter was also in literally every deck for only 3 mana.
There was never a chance for this card to be a game winning play. 6/7 for 5 mana is really just a "cute" combo that would still prob get silenced or in the case of face decks simply ignored.
Today's Meta could definitely see Bolvar as being very playable in a deck like Secret Paladin.
I think this card has potential to be a situational 1-off in a battlecry heavy tempo deck such as Dragon Priest.
Arcane Giant looked terrible at first, but then it turned out to be a great card. Having the ability to remove a major threat and then drop an 8/8 same turn late game is a game winning play.