Lag when using real cron job for multisite

I’m using a real cronjob on a large multisite that has over 200 blogs. So I made a cronjob for each of subsite with this command:
wget -q -O - http://www.yourwebsite.com/wp-cron.php?doing_wp_cron >/dev/null 2>&1
The problem is when it runs all 200 cronjobs it lags the server. Is there a better way to manage a large multisite to run a real cronjob? something that doesn’t lag the server