The only card I can think of that makes it good is Power Overwhelming where you can then keep the stats, but even then you have Void Terror and Faceless Shambler that do it for cheaper. Really, the card just sucks compared to most other options. The only advantage it has over either of the other two is that when silenced, it has better stats than them.
I got it in my ftp account and used it in a totem shaman deck: played it to buff my Mana Tide Totem and my Flametongue Totem respectively. It did take my opponents longer than usual to deal with them, but I didn't feel like it was a match-deciding move in either case. And then I got a golden Evolve in a pack and the totems went out the window along with the Darkspeaker lol.
I also tried it in a priest deck, but not for very long; I thought somehow that it would buff my Northshire Cleric, but even my ftp Priest has way better card options at the moment.
It has many combo uses I think. Problem is it is so situational that it's probably safer to run a more mindless card most of the times. I guess the high mana cost is what makes it hard to efficiently combo. This plus rarity makes it a very underused card during early expansion stages either. Maybe it will become more common as more people drop them from packs.
Meta cant support this type of slow, board-dependent, situational combo card. I mean you only have 30 spots in your deck. There's ALWAYS going to be something better than this, despite all the fun shenanigans listed above in this thread.
i though to combo him with Validated Doomsayer , you play validated. next turn ( as a 7/7) you atack with him andafter that changestats with darkspeaker. Your next turn you have 2 7 attack minions. But is only theorycraft not try it in real situations.
it is good to save cards that on the edge of dying like Ysera or ragnaros imagine that your Ysera have 1 or 2 hp you can swap stats and Ragnaros the Firelord you can save it. Or you can give Angry Chicken 3-6 or you can use it with warior cards there is too much possible usage for it