so I went out and hit about 60 systems in Outbreak and not only were there but a few HGEs I only found one system that provided an HGE with Pharmaceutical Isolators - just one That will surely kill anyone's desire to engineer their ship I understand we have Material Traders - good thing - but the ratio I just mentioned is ludicrous
The spawn rates can vary, I was farming them not too long ago and found it was best to try to find a system with the correct requirements but also with only a few planets etc.. I would also check out the Encoded Emissions too as they turn up good mats and thought it was a good way to push the game into spawning new signal sources. Sometimes they were hardly spawning but there were other times where there were quite a few giving good enough quantities of Pharmaceutical Isolaters that it wasn't too much trouble to max out my storage.
Having said that, if you're looking to fill up in ten minutes or so then obviously you will be disappointed. I would hang out and use the FSS to scope out all the sources in the system and go from there. Treat it like a chill mining session.
But then, also, I enjoyed mining in Minecraft and found it very relaxing to do, my son doesn't enjoy it that much but it evened out as there were things he liked doing that I wasn't so keen on. Like mostly using my mined diamonds etc...

Anyway, it's one of the reasons why I think all materials should be tradable between players in game - by using the fleet carrier trading buy/sell system and just letting people drop them from their inventory either on foot or from their SRV. It helps with the overall balance I think as it can allow different types of players to help each other when it comes to activities that one group is averse to but the other one is fine with.