Macintosh Lag with multi-client MAC

What mac are you using? What are the specs?

First, I'd check if it's a local performance issue:

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Check Mac computer performance

1. To access the Activity Monitor go to Finder, Applications, Utilities. Click Activity Monitor.
2. Choose the process category you'd like to check on. You can choose from CPU, Memory, Energy, Disk, Network, and Cache.
3. You can then choose how much information to display and in what format.

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Are there any indications that you're hardware is at capacity?

 

Are you running MapleLegends (via Crossover) in this screenshot? I'm wondering how the performance chart in this screenshot would compare if you were to take the same screenshot running multiple clients. My guess is there'll be strain on the CPU / RAM?

 

Thanks for the screenshots! Looks like your storage, and RAM are good.

Though, when running two clients you are utilizing a high percentage of your CPU. I'm assuming that's correlated with your performance/lag issues, but I can't say for certain. Might be worth trying to turn down the graphics, and seeing if that has any improvements on performance.

It's quite interesting that your blizzard skill causes 20 seconds of lag as mentioned in the OP, since that certainly sounds to me like a network issue.

Wish I could help more!