I doubt the veracity of that statement considering that Aard at high intensity gives out free insta-kills like candy

No I'm not trying to demean anyone. I've tried and tested most builds. Pure signs being trash compared to the other builds is just my opinion, not trying to hurt your feelings.

I doubt the veracity of that statement considering that Aard at high intensity gives out free insta-kills

most of the tier 3 and 4 skills are completely useless. And if you read my post, I said aard is a really great skill BUT it's capped. Getting 200-300% sign intensity isn't going to do that much except keep enemies down longer than required. And it's completely useless against a lot of the tougher enemies in the game, Eredin, Olgierd, Imlerith, The Toad, etc. It's great against mobs, gives insta kills but what are mobs compared to the toughest bosses in the game?

Quen being a shield that can let you regain health whenever you want regardless of toxicity or food,

Alt-quen is decent early on but once you spend 3 points in acquired tolerance, you don't really need it, Just pop the ekhidna decoction which works great with every build. Spamming signs will heal you and you won't be forced to hold a shield like alternate quen

Axii can be in either form.

Puppet is a really good skill in death march. But it's completely useless like Aard against most of the tougher bosses in the game

You are really underselling signs. This is not a multiplayer game,

Not underselling signs. I've played a majority of my first build with a sign build. Going PURE signs is just trash, you need sword damage, you need decoctions if you're looking for a good build which is what you asked in the first place.

Using alt-quen, puppet, aard, and igni is good for support. But just focusing your build solely on those will leave you with no damage and you'll be fucked against bosses who are resistant to signs, which are a lot of them.

You can beat the game with any build, going ALL signs weak. Calling it trash offends some apparently.