Not legally, no. Any work published online is subject to copyright. That includes resource packs. As a rule of thumb: if you didn't make it from scratch and don't have permission from whoever did then you are NOT allowed to share it online.
As to whether or not you'd be sued... that's not up to me. It's up to the rights holders of the packs you've mixed. They definitely can file a cease and desist against you should you attempt to share their work without their permission. More than likely you'll just get banned from whatever site you upload your mix to, though. But again, that's for the creators and their lawyers to decide an not anything that I have any input into. (Well... except in so much as I try to remove any infringing works from this forum before the rights holders and/or their lawyers see it. DMCA Safe Harbor provisions and all that.)
Honestly if you really want to publish your mix it's just a lot safer to actually secure permission from the contributing artists. That way you won't have to worry. Remember that on this forum you need to post proof that you've obtained permission in order for it to count. That's very important.
I hope that helps you.