It's not really broken - not in the same way that "Infinite Gandalf" or "Fruit Loops" is broken. If you have to build an entire deck around a combo, it's probably not broken unless it's auto-win. This may give you a massive move limit - but it wouldn't stop the shadow player from killing you. Nor could you win in one turn, probably not even two. And a 1-3, 3-6, 6-9 move is possible with just Raddy.
If anyone makes an 'unbeatable' deck around this combo, we can talk about changing rulings and stuff.
I think they ruled it the way it did to avoid any confusion about making the move limit -1 if
Radagast died and was discarded... and the possibility of having to make a different ruling if a move limit of -1 was reached (which would be possible if the move limit was made -1 when Raddy died). It may be a bit weird, but nothing game-breaking, surely.
EDIT: NK, the battleground text of Gandy's Hat makes that combo waaaaaaay too out there. Unless you can manage 3+ burdens each move...