I don't know what happened in your games with the priests but if your running that many assault marines then you really should reconsider and take a couple, at the very least one.
They make your guys survive literally twice as many small arms and standard CC attacks, plus the furios charge boost should allow you to wipe out most of the enemy unit before they get to hit you back when charging. Obviously placement of your priests when assaulting is critical and you need to make sure that you never get into base to base with anyone with a power weapon.
If you play against alot of dark eldar or possibly some eldar lists then I can see you may have issues with them getting the charge on you and out initiativing you but even then if you've hidden your priest at the back of the unit you should be able to place him so he recieves a small amount of attacks.
The other way to make sure they stay alive is to not get them into combat but still keep them within 6" of the units you want to effect with his abilities.
There a various ways to do this, you can get him to leave the unit before it assaults or sit him in a vehicle nearby to your units so he can measure his power from the vehicles hull and effect many units.
Another slightly trickier tactic that I like to use is to keep him with the unit but put him at the back and far enough away that he can't make it to combat. It takes a little bit of range guessing but when done right you can have the unit he is joined to launch an assault but have him fail to reach the combat, as long as you make sure none of the enemy models can get to him with their defenders reaction move he'll be perfectly safe with noone allowed to direct attacks at him but remeber that he also wont be able to attack back.
After that rather long point back to you list
I'd find the points for a jump pack for the libby, much more reliable than wings that you can fail to cast or have cancelled by anti-psykic stuff which would slow down his whole unit. You can then get either an aditional CC power like the one that gives S10 or perhaps the one that gives a cover save to all friendly units nearby.
The big assault squads look good (but need priests) the small ones don't need the power fists.
The dev squads are ok with one las as you can give it the +1BS from the sarg but they would probably be better if they all had the same weapons. It might be worth changing one or two units of these to either preds or vindicators as I find theres not always good places to set up three backfield shooty units but your statagy might not allow for this. A couple of Vindicators are especially good if you take the cover save power with you libby and advance you assault marines up field behind the vindy wall granting them the save whilst keeping your marines out of sight.