There's a few things you can do to help with raiding:
- Consider optimizing your HUD. Move important information closer to the center of your screen and less important information further away. This helps it so you don't have to keep looking all over the place to keep tabs on what's going on. Can even make a separate raiding HUD preset and hide some of the information or hot bars you don't need in raids.
- Turn down spell effects. I forget where exactly the setting is, but you can set it to show only important spell effects from your party members and no spell effects from those outside your party. I have some macros set up so I can quickly swap between shiny light spam and clean reduced spell effects when I actually need to see what's going on.
- Consider rearranging your hot bar. Sometimes you get used to pianoing your fingers across your keyboard and don't realize there's some commonly used spells and abilities you can move over to be more accessible. If you want to go even further, you can consider upgrading your peripherals. I really like having an MMO mouse with the 12 buttons on the side. I have it mapped to my hot bars so I can cast everything with my thumb on my mouse plus maybe a modifier key.
- Given all of that, a fair bit of it comes down to just learning. As you learn and get better at your rotation you have to spend less time focusing on what to press when and you get a better feel for your cool downs without having to watch the timer as closely. And as you do a fight more and more you just get used to not only what's happening but also what's coming up which allows you to potion and plan accordingly.