Tip 8: Low FPS FTL
When raid AoE starts crashing in if your Frames Per Second fall to single digits most likely your computer needs some upgrading. Anything under 30FPS is probably going to affect your DPS -- from minor, to major, to severe. Most raiders will be getting 60FPS. 60FPS is a high quality video on the internet. 30FPS is a standard quality video. You can think of numbers below 29.875 as degraded. Often sound doesn't synchronize with the video. If you are getting 30FPS you probably need to have your enhanced video settings (dimensions, shadows, spell effects, etc) turned down. Maybe you already do. Spell effects are important. Make sure your setting allows you to see the fire you are standing in. The color and effects of the fire vary all the time. So does the floor color. Experiment. Seek guild advice. Don't run in windowed mode. That will lower your FPS. Don't run in max resolution. Knock it down for a speeder response.
If you have adjusted your video settings and you're still below 30 while in an active raid, then you can use this completely made up rule of thumb to see your DPS penalty: for every 3 FPS below 30, you will be doing 10% less damage than if you were at or above 30. When you're at 0 FPS you'll be at zero DPS. Okay, maybe that heuristic is crap, but you get the idea.
If you are still out of luck with tuning settings down, ask a knowledable person what you should upgrade on your computer. It could even potentially be a bad router, hub, or faulty NIC. But generally, you'll want to upgrade your computer RAM, video card, and CPU in that order of priority.