In my experience, Relic has a handful of testers who do play the game but they're not necessarily good enough at the game to play on a high level. This is why they often seek feedback of high level players. This isn't always a good thing, because pros play the game in a very different fashion than everyone else. However in my time with Dawn of War 2 I ran into a few Relic devs in automatch. Most of the time they were just testing something and then surrendered though.
They do however have a bad habit of not testing their shit before releasing it. (Or otherwise having some issues with build management internally) There was a fun bug in Dawn of War 2 that involved a character being rendered as a black box when equipping a specific upgrade. It was caused by them adding a helmet that was supposed to render when equipping this item, and it took two separate hotfixes to fix it. Most likely this was caused by a mismatch between the internal build and their external build but it was pretty funny at the time.
That is the problem with Relic, more than any other company, they give me the idea that they are incompetent.
I think their biggest problem is that there's such a lack of internal organization and direction.
For example in Dawn of War 2 there's a flag called ability_knockback which unlike normal knockback would work against retreating units. They'd come out and say "We want to get rid of all instances of ability_knockback!" and there'd always be some niggling here and there. And then everytime an expansion came out all the fucking new units used ability_knockback for a few patches.
It was a huge jumble of people working on the campaign, the last stand and multiplayer which all had their own stats and rules. It never felt like there was any care put into how things were balanced and that everything was a kneejerk reaction to community feedback or a misguided implementation in the first place.
They've doubled down on "listen to the community" with CoH2 which has resulted in them abandoning the eastern front, blizzards, most of coldtech and design decisions (old vp bleed, ostheer etc)) in favour of making the game more like CoH1.