Sure, it happens frequently in other games, and it happens frequently here. But that doesn't mean that there are game systems for this elsewhere, nor does it mean that there ought to be game systems here for this.
In WoW, I know of no mechanic that allows for what the OP is requesting. Nor do I know of any such mechanic in EQ or EQII or LotRO or AoC or DCU or CO or STO or... actually, no games do that, that I know of.
This is utter nonsense. If you engage in a trade with another character, and they somehow found a way to hack the game and force the trade window to cheat you... then sure, devs would step in. But if you get a random stranger to promise to make you something, and you send that total stranger some materials in advance, and then that total stranger rips you off... it's all on you. It's up to you to make sure that your trades are fair. That's not the devs' business, nor should it be. They have other things to spend their time on, besides mediating between parties in trades.
The bottom line is always CAVEAT EMPTOR: "Let the buyer beware". It's your responsibility to ensure that you're happy with the details of the trade. And again, other than hacking or other explicit cheating, the devs have nothing to do with this sort of thing, here or in any other game.
Hardly. I've played over two dozen MMOs in the last thirteen years. At no point, in any of those games, have I felt that it would be wise or prudent to send cash or valuables to a stranger. In all cases, I either dealt with friends, or over the AH, or arranged to buy a finished product (for which I might pay cash or materials or some combination thereof). And I've never experienced this as a problem; I'd do the same in real life, after all.
I'm genuinely sorry the OP went through this. I'm not being callous; I don't enjoy the suffering of others. But the OP was foolish and the devs are not responsible for that. Sorry. Next time, please be more careful. That's all that anyone can offer you here: good advice, well intended.
In WoW, if you engaged in a trade transaction through chat, and you are ripped off, and you report it, there will be an investigation and if the investigation shows you got ripped off, you will get your items back and the offender will be punished. I know this as fact as having had it happen to me. Chat logs showed what was agreed to and trade logs showed what was traded.
It is little different than agreeing to a loot system in pre-made groups only to have the loot distributor go against the agreed upon rules and give an item won by roll to his buddy instead of the roll winner.
Simply put, a system IS in place in WoW to prevent these types of actions.