LOL! Bro, you just brought back some fun memories from when I used to play Mortal Combat. FATALITY! LMAO!! Good one.
I've had good luck with Wicked Sensations and the dkp kernel. After tweaking the kernel, I've actually gotten very good battery life from that ROM. One thing that I have noticed is that Xposed Framework, with a good bit of its mods running , will drain the battery faster.
Have you tried Wicked Sensations?
Other things that I do to help with battery drain are to tweak the wifi settings. I turn off most of those options. One of the main options that will pull juice is the one that keeps the phone constantly looking for a wifi signal. I turn that one off. GPS is another that I disable unless it's needed. There are the other little tweaks like freezing apps which you mentioned. Lowering the screen brightness is another battery saver I use when I'm out and about. As long as I don't stay on the phone all the time, battery drain isn't very bad.
Unfortunately, staying off the phone isn't an easy thing for me to sometimes. I'm very thankful a good friend sent me one of his Zerolemon batteries. Even with heavy use, using the battery saving tweaks usually gets me quite a few days out of one charge.
Just using the OEM stock battery, it takes me 2 to get through the day with very heavy usage. I'll usually use 1 and half of the other.
You mentioned the M8. I've actually read several posts here at AF and over at XDA where members were talking about this phone. I have yet to see it. As soon as I finish this post I'm going to check it out and read up on its specs. It must be a nice one.
EDIT:
I just read up on the HTC One M8. Wow! A very nice phone indeed. I like the boomsound speaker set up as well as the brushed aluminum case. Too bad that that beautiful case won't be seen because most owners will wrap it in a case. I don't blame them either because that sucker is expensive! Even if Boost ended up with this phone I doubt very seriously I would even be able to afford it. It's a very nice device. Sadly, the price tag reflects just how nice it is. LOL.
I'm very happy with my S3 and have a good feeling this will be my daily driver for several years to come unless something unforseen happens. One things for sure, there's still a good bit of development going on for this phone and I hope it continues.