I disagree that Ruth Westmacott is unimpressive. I think she's pretty darn good, and well worth the 3XP for Charisma to run both her and Alyssa Graham. (Of course you want Alyssa - she's the single most important card for Gloria). Yes there is the risk in Charisma-for-Ruth that you don't draw her, but Charisma for an optional signature ally tends to open up campaign-specific allies too, and then you play out which one you draw. Let's assume for now that you get Ruth out alongside Alyssa - is Ruth worth that 3XP and 3 resources? Wholeheartedly, yes.
The trick with Ruth is to be using her a lot. With Gloria, you don't just want to lock down a few Ancient Evils or whatever into your basement and then leave it at that. With Ruth out, you want to be cycling cards into and out of the basement every turn, possibly even multiple times / turn if you can.
There are no limits to how often you can use Gloria's ability. With Alyssa out, you've got one every turn. With Scrying(3), Scroll of Secrets, maybe even Parallel Fates or First Watch , or even her Elder Sign / Seal of the Elder Sign, getting two cards into the basement in a given turn isn't hard. It doesn't even have to be every turn, you just want a steady flow of cards in. Then Ruth allows you to flow the cards out again, claiming her bonus.
Ruth's bonus is actually pretty good. It can reduce skill tests to 0, it can make "fail by X" cards (like Rotting Remains) completely blunted, it can be used anywhere on the map, and it doesn't exhaust. If you've seen Liber Omnium Finium, then you can safely be flowing monsters through Ruth for auto-evades or fights as well. Just getting the bonus, say, 3 or 4 times and burning her for Health/Sanity would have been worth the play. But you can do it far more often than that. In my most 4-player recent game, I dropped Ruth first turn alongside Scrying (3), getting Alyssa online later. By the end of the game, I'd used Ruth 14 times. Even if you say it's half as good as Ward of Protection, that means Ruth deployed 7 Ward of Protections for 3XP, 1 card, 3 resources - that's insane value!
Yes, she's better the more players you have. But that's OK, as Gloria's main abilities are better the fewer players you have. So Ruth can help across the board on 3/4 player, but is still good on 1-2 player. We'll see how Gloria's "real" signatures turn out, but for now, I'm very happy with Ruth.