Galaxy Nexus is very slow and laggy and refuses to be any faster

I've had my galaxy nexus for a while and i've put up with the slow response and lag up until now. Most of my apps take forever to use and other just don't even work anymore because there's too much lag. If i even have more than 1 or 2 apps opened, my phone (for whatever reason) just can't handle it, heats up like crazy, and just drains so much battery that I have to take out my battery and wait for a few minutes just so to let it cool down and reset it.

I've tried a few of the better options which is to root my device, get slimkat android 4.4.4 (which kind of worked), and get lagfix premium along with greenify. But after all of that and trying a few other options, my phone is still as slow and laggy as ever. what else is there that i can do? If I need to provide any other information on my phone, let me know and I will reply.

laggy camera lp5.1.1

Is it just me or my Dad's C6903 running kitkat 4.2.2 has a lot smoother camera viewfinder ( good refresh rate) as compared to my C6902 running latest lollipop 5.1.1?
Both the phones are non rooted and running stock Roms.

I recently brought the phone from a friend of mime and directly updated to 5.02.Couldnt comapre both phones.

Many people are facing this issue and videos are posted on youtube showing slower refresh rates of 5.02/5.1.1 xpedia Z1

OG LAGGY

Installed OG on my phone 5 days ago and it started to get really laggy yesterday. Requires me to restart the phone multiple times a day. I Odin the tar and wiped everything. Did not root. Any solution to make the phone better without rooting?