I just got a SD 744t recorder, and I'm trying to decide whether I should record g3 lavs directly into the recorder (through the ta3 inputs on 3/4), or whether to go g3->302mixer->744t.

The only thing I really get from having the 302 in the system is the ability to adjust levels easily for the lav record level, and another limiter in the system.

Personally, I'm of the opinion that it's best not to ride the gain on wireless; you aren't going to stop clipping at the transmitter by adjusting the post-receiver gain, and the 744t has a much lower noise floor than the g3 system. So the only reason to ride gains after the wireless system is set up properly would be to help the editor out.

Am I missing something... why do I usually see people using 552 mixers with the 744t? Is it just to have gain adjustment dials or are they doing actual mixes?

A 552 is a mixer, and a 744T is a recorder.

When people use a 552 + 744T combo, they usually mix out of the 552 to camera and record individual pre-fader tracks to the 744T as a backup or or the isos. It also allows better monitoring amongst other things.

I used a 302 + 744T combo for many years.

I also have a 302/744 set. (but not for long)
Generally, I use the 302's preamps/faders for boom or other gain ride mics and the 744s internal preamps for lavs.

I finished a 2 day shoot with just the 744t The gain on the 744t line inputs had to be turned up to the max 18db gain in order to hit full scale when the g3 does, whereas the 302 has plenty more gain.

The main reason I found myself wanting the 302 was that there was no high pass on the g3 line inputs otherwise.

Another issue is that every now and then I get static coming from a lav going out of range, and I need a way to mute that as quickly as possible so my headphones don't destroy my ears. Spinning the gain down or even powering off the 302 is a quick way to do that. The 744t doesn't seem to have a single-control quick way to mute loud inputs, except pressing play which is my global kill button now.

The G3 receiver's AF parameter needs to be set to the max to output an adequate signal for +4dB operation. There are a number of ways to monitor the 302 and /or 744. No quick and easy way to mute a wireless output or input.