Zomar, I've got to disagree with you here. REBs are awesome in Goblins! The biggest threats to Goblins are blue spells, so REBs and Pyroblasts are just the shit. However, I gain from your post that you're playing some type of turn 1-3 combo deck, since you mention going off before goblins.
Anyway though, I think that decks such as the one that you mentioned need probably something around 2 appearances in major tournament T8s or perhaps just a consistent T8 performance in an area over several months before they'll get more than a handful of people who are confident in their abilities and thus consider them part of the "gauntlet" to test against.
REBs in aggro decks always have their ups and downs. The main concern of any aggro deck is Tinker. More games against aggro are ended by tinker than in any other way. If an aggro deck can stop tinker, they have a very good chance of winning the game. The problem with REBs in aggro though is that they are reactive cards. It's in aggro's nature to play things at sorcery speed, to tap out during its turn. In order to play REB you need to hold back a mountain, by holding back a land, you aren't dropping threats. This leaves the aggro player with two options: dedicate the first 1 or 2 turns playing threats and then keep mana open for REB while beating them down, or constantly keep 1 mana open and drop 1cc guys on turn 2, 2cc on turn 3, etc. Neither of these options is fullproof. By dropping threats first, you are giving your opponent crucial time to get tinker, or do something else broken. With the increase of tutors, turn 2 tinkers are all the more prevalent. But if you hold back mana, you are also giving your opponent more time to win the game. You must also consider that your opponent will typically have more counters than you, therefor if they force your REB which you were keeping open instead of playing guys, you in a terrible situation as you essentially gave your opponent extra turns.
Perhaps what I said before was unclear, I don't think REB is a
bad card in FCG, it's just that I don't think it's a good one. It has good synergy with lackey as you won't be forced to tap out with guys. If you don't draw lackey, I don't think you will be able to play it before turn 3-4. Turn two is when piledriver and recruiter comes down, not dropping them to keep REB open is a mistake in that the longer you wait, the harder it will be to win. The downside of it possibly being a dead card isn't too great, because you already have a good matchup against most non-blue decks. It's definitely good in that it can by you an extra turn or two to win the game, but I don't think it should be included without serious look into its usefulness and without playtesting. There was an old saying about FCG: other than the food chains and the mana, the rest should be goblins. The only other considered card was wheel of fortune, but giving seven to your opponent proved too dangerous. I don't know if that saying holds true anymore. Red decks might be forced to play REB main now as almost a staple card.
Going back to what Gabe said about DSC not being fast enough against FCG in control. A hand that lets you find/cast tinker and has a force of will should be enough to race them straight out (the force being for countering some random dangerous spell, thus giving you time to win). That's just as likely as your opponent having a fast opening with recruiter/foodchain or piledriver + swing for a lot early on.
As the game goes on longer and the control player gets a decent amount of mana, goblins loses as nothing stops pentavus. If you're not playing pentavus then you are playing oath, which stomps FCG anyway, or gifts. If you are playing gifts, well, I hope you lose.
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Oh about the decks I play: shitty ones like sex, the mountains win again, enter the dragon, and cherry parfait. Before I was talking from the perspective of a typical control or combo deck.