First of all, are you on the pc or the consoles?? The pc group finder is indeed bad, but many people use /zone chat instead. On the console there are known issues with it that are on the list of things they are going to fix.

I personally find it best and easiest to find a dungeon group in guilds.

I´m sorry. I´m on Consoles PS4 btw.

Most people don´t use mic. The other night i got invited by someone, and we spent literally 30 minutes asking to the people who pass by if they would join to do the dungeon. Most didn´t answer and those who did were already on a group.

So far if you don´t have a friends group this game is very Single player focus.

Had a great time on Cydoril, though. Following the commands from someone who take the lead role. (died very often though)

Unfortunately, Group Finder on consoles is currently a joke. Your best bet is either what you're doing now (waiting outside dungeons and inviting randoms), though as you stated it's time-consuming, or joining a guild that runs dungeons. I know the Guild Recruitment section on these forums is pretty active, so try posting there for an invite. Once you make a few friends, it'll be easier.

There are also a few 3rd party LFG sites you can try:

http://www.esotulfg.com/

https://www.eso-lfg.com/en/

https://m.reddit.com/r/ESOTULFG

Hope that helps