This is not the answer you are looking for, because I am going to try and dissuade you from this (which is actually the only rational answer).
On my raspberry I really don't need crons and pam logging and I want to have less i/o to make the SD card life a little longer..
If you think cron is truly doing excessive logging, then you should consider what cron is doing and how often, and tweak that. Point being, if you don't care much about what it is doing, then why is it doing it?
WRT SD cards, logging is not significant enough to worry about. As in: totally insignificant, you are wasting your time thinking about it. SD cards use wear leveling to help preserve themselves: they don't suffer the effects of fragmentation (i.e. fragmentation is irrelevant to performance), and when you write to disk, the data is written to the least used part of the card, where ever that is. This transcends partition boundaries, so if you have a 2GB partition on a 16GB card, the partition is not limited to a 2GB wide block of physical addresses: it is a dynamic 2GB whose physical addresses will be a non-contiguous, ever-changing list encompassing the entire card.
If your system writes a MB of logs a day (you can check this by sending a copy of everything to one file, which is often what /var/log/syslog is), and you have a 4 GB card, it will take 4000 days before such a cycle has written to the entire card just once. The actual lifespan of an SD card might be as much as 100,000 write cycles [but see comments]. So all that logging will wear the card out in 4000 * 100000 / 365 =
~ 1 million years
Do you see now why reducing logging by 25%, or 50%, or even 99%, will be completely irrelevant? Even if the card has an incredibly bad lifespan in terms of write cycles -- say, 100 -- you will still get centuries of logging out of it. For a more in-depth test demonstration of this principle, see here.
Basically, all I want to log is fatals, hardware stuff, kernel/dmesg, and failed logins
Unless you enable "debug" level logging, by far the thing that will write the most to your logs is when something has gone really wrong, and generally those are going to go in as high priority unless you just disable logging entirely. For example, I doubt under normal circumstances that your pi, using the default raspbian config, writes 1 MB a day of logs, even if it is on 24/7. Let's round it up to that. Now say a defective kernel module writes the same 100 byte "emergency" panic message 50 times per second to syslog on an unattended system for one week: 100 * 50 * 60 * 60 * 24 * 7 = ~ 30 MB. Consider that in relation to the aforementioned lifetime of the card, and the fact that you probably want to get the message.
Logging that haywire is very unusual, BTW. Logging is good. The logs are your friends. If you want to tinker with the rsyslog configuration, your time will be better spend adding more, not less.
