Well, a great batrep, good to see the orks in action.
As you have found out orks die by the handful, so that is why the best upgrade for an ork is more orks...
The shoota boys should be in a truck, so you can drive around and do some drive by shootings, great fun. Make sure to give the truck a grot for the it will not die rule, and the truck will last all game (unless your dice roll too low).
OH, wait, your a kan wall player
Get the shoota boys a nob with the big choppa and use the boys as wounds to get the nob into combat. Two squads of 12-15 shoota boys is a great way to play. 24-30 shots even with bs2 will get something. Make sure that your nice and close so the boys don't miss too much, and what doesn't get killed by shooting you can charge and give em a good ol fashioned krumpin.
As for the kans, always have a unit of boys nearby to bail them out of trouble. The grotzookas are great weapons (for orks) and this should be the only shooty unit you use that doesn't get into combat until it is time to take an objective.
I also agree with the above posters, the mek should be split off into his own squad. Put the lootas is a battle wagon for rolling cover. Make the mek with his wdtd (what does this do?) gun in a empty spot with some grots so he doesn't blow up any boys. I have had terrible luck with the shock attack gun, and so I took it off the mek and made him into a kustom model with other weapons.
As for going faster, I recommend that you get buggies before death coptas. Kit them out with TL rockits and go blow stuff up. They have the same outflank as the coptas with the advantage of not taking LD tests after one of them dies. Sure coptas have a jink save but unless you have "special" dice the coptas will take one or two casualties and then leave the board. While buggies will stay till the last drop of squig juice. Plus you can give buggies skorchas (rockits are better) to roll around a flame stuff is great fun, and after a three or four template skorching, your opponent will make that unit a priority to kill and leave the rest of your army untouched. So you can then get nice and close to give them a krumping.
Congrats on a good game and may you have many more good krumpings