I only mention the possibility of variety because if you feel your build is lacking something due to not having ascended, its probably lacking due to other reasons (ascended makes a small difference really).
As i said, in my experience pure carrion gear is not the ideal condition setup. Yea, it will work fine, but like you say, it will feel lacking.
Have you tried other condition builds? like one that is based on prec/toughness instead of power/vit? Or a mix of the two?
I did try some playing around with it last night in sPvP. And I will admit, it was a little more tanky, balancing out the gear with some toughness. However, the 1 stack of bleed with that crit sigil only 60% of the time is hardly enough to actually try and stack precision. (This is just what I saw from last night's testing)
Right now, I run a 0/0/30/20/20 condition build. And would prefer it stays like that. However, I'm open to try something else. I'm just having a tough time really making anything else function. I already have a hard enough time going against tanky guardians ect, so I'm trying to keep my damage up.
I was considering using the runes that offer condition damage and toughness. (I forget the name, I had used then in sPvP) and they seemed rather nice. Hmm I'm not sure. Would love to interact with other P/D condition thieves and see what they run.