Cowardly was broken in the last update, it now causes nothing to be discarded. I have seen this happen with raging strike, powerful hack, and obliterating chop. When you click the drawback, it cycles, but there is no effect.
I've heard rumors that the same is true of superstitious, which I believe is the only other drawback which causes discard, but have not used superstitious myself since the patch.
Dropped Guard also doesn't discard at least armor, reported here. Seems like all card discarding of traits has stopped working.
This needs to be fixed ASAP. Every MP game I've played today has been against people running 2-3 warriors, abusing this by getting crazy cycling from taking cards like superstitious, cowardly, etc to get crazy cycling. It really sucks. EDIT: From what I can tell, Superstitious is still working.
Pretty sure this is something that they could hotfix - not even sure how this could have been broken with the current changes. However, it's the weekend - so I wouldn't expect anything before monday, unless we get lucky. Hang in there people.
Oops, totally forgot about dropped guard, good catch Jarmo. Yeah, it would be nice to see a hotfix for this. I haven't really seen much abuse of it thankfully. I'm not using them in the hopes that most people won't notice.