There's different levels of each stat. It's not just a high vs. low thing, there's nuances inbetween. Having useful stats, is useful. Poor is only useful if you want to intentionally suck at things. Some folks like the challenge. I wouldn't, but hey it's a twist on the rp.
Average should be considered - average. Sadly, players often confuse average with "I can't play with this because it's not good." If I were playing a mage, I'd want my wisdom to be better than average, but I wouldn't whine if it wasn't AI. As a warrior or combat-heavy character, "above average" strength would probably be the least I'd want to play. Perfectly serviceable, just not impressive. And hey, if I had really good dexterity, I'd be faster than someone who didn't. So I might not hit hard, but I'd hit faster, thus moving the challenge closer to equal. Afterall - if it takes you 3 seconds to give me a single 20-hp hit, and takes me the same 3 seconds to give you two 10-hp hits, the end result is the same.
Stats count. Absolutely. They wouldn't be coded into the game if they didn't count for something. And the lowest stat is absolutely going to hurt, when you rely on stats to be functional in a skill that uses that stat. But if you rely on being amazingly awesome at one or two single skills to be a "viable" character, then I'd suggest you broaden your expectations a bit.
Maybe you're just "competent" with a sword and have a tough time wearing the heavy armor because of lousy agility, but you can kick ass unarmed and bash like a champ because of high strength. (No I don't know which stats have the most affect on which skills, this is hypothetical. Insert whichever appropriate stats and skills are involved and repeat the sentence with the new interpretation. Point stands).
If you have below average on ALL your stats, well you do get a reroll out of chargen. If they're still below average you can send a request to staff and ask if they might give you a hand up so the grind is less of a challenge. An "all average" character is 100% viable. Not optimal, but viable.