The way the math works out, lightning claws result in more wounds than swords against most opponents, even with one less attack. They're both ap3 so as a general rule: never take power swords! They are equivalent cost on all but terminators. Look at it this way: re-rolling a failed to-wound is equivalent to getting an extra power sword attack that auto-hits!
For the terminators, yes power swords are free, but so are power axes! You've got the 2+/4++ to survive long enough to swing them. S5 ap2 is a huge upgrade. Especially given the biggest assault threats have a 2+ armor save.
for a moment. Rhinos and meltaguns are a great loadout for CSM. As they will be charging forward I would give them extra ccws as well! Marines with 1 attack are pretty terrible in combat. Also you need the heavy hitting anti-armor in your list that the meltas bring. A melta bomb on each champion is pretty essential as well for big stuff.
For the terminators, I always prefer more combi-weapons to the reaper autocannon. It's too expensive and gives your unit a bit of a split-personality disorder.
I'd also really try to squeeze in a powerfist in addition to the claw for the lord so he can get his ap2 on and threaten vehicles/monstrous creatures.
As for radical changes, You could mark your lord nurgle instead of tzeench. This would allow you to swap the nurgle marked marines for real plague marines which are point for point better at everything but having more bolters. I'm not sure where you'd be at points-wise but you'd probably have to leave the terminators unmarked.
The last thing I'll say is that you don't need a special close combat weapon in every unit. Learn to trust in weight of wounds. People do fail armor saves ;).
Not a bad start at all.