Yes, it may be considered high for those with older hardware (e.g. less than 4GB of RAM). Adguard (and it's service process) are probably using higher memory due to all the filtering it has to do for each web page/tab opened in your browser(s) of choice.
With that said, my Adguard.exe is using around 40MB, depending on how many tabs I have open. AdguardSvc.exe uses about 110MB with multiple browsers and tabs open. So all-in-all that's about 150MB usage while using Chrome, Chromium, Firefox and Nightly with multiple tabs open in each. Personally, I'm not too concerned about that as Firefox, Chrome and Internet Explorer easily exceed that amount of RAM with the number of tabs I'm usually running in each browser. That, and I have 16GB of memory.