meltabombs for walkers

, you have a point though.
Transportation and mech is where it is at. Go for rhinos or the razorbacks. It is just needed.
Having 2ML and 2 plasma
dev. squad is the thing to do here. Also the combimelta serg. would be good for a tactical squad.
Captains are rarely better than librarians. A plain librarian will do you well.
Assault squads are pretty bad.
If you take out the assault squad for 2 razorbacks with let's say las/
plas turrets and then you will on to a very reasonable list.
2 razorbacks and dread going forward with 6 heavy weapons giving covering fire is pretty good.