I can tell you as an avid player in the PVP, it has always been that bad. Since DS1, since DS2, since DS3's launch. If anything, more players are cooping or actively ganking these days and it's actually a fairly terrible experience for invaders with a lot of factors placed against them. I blame no invader for pulling off the stunts they do. If I come across an invader like that and they just run off, I'll shrug it off and continue playing like I was before. If I run across them again later in the level, they will be dealt with then.
As the world host you have a number of different options in how you can deal with invaders. The primary one being summoning, specifically, the Way of the Blue. The covenant is specifically designed to bring Blue Sentinels and Darkmoon Blades into your world to track down the invader. They usually don't take long to come pouring into your world to help. It's also nice you wear that covenant since the sentinels (like me) need all of the summons they can get since it's the only way they can actively go after invaders. It's the perfect covenant for someone such as yourself.
You can also try going back to bonfires and looking for a coop summon there or use other utilities like the giant seed to turn enemies against invaders, albeit it's a bit nerfed now.
Overall, I get your complaints, but at the same time, as someone who used to invade a lot, I still sympathesize more with invaders. The ultimate solution if you hate it so much is don't ember or go offline. If you're cooping actively with someone you have absolutely nothing to get worked up over with invaders. You have an incredible advantage over them when cooping as most of the time the invader will die when outnumbered. Play through the level and eventually the invader will die. Most of the time it will end that way unless the invader gets lucky.
