Except that with some weapons, particularly the cane, this is a really bad idea. The whip in particular trains you to stay away with your attacks, because it has a long windup and cooldown, but is useful because it has an extremely wide and long-range attack. With weapons that can have super armor like the Kirkhammer, the behavior you describe is useful. But with other weapons, learning this often doesn’t benefit you (in fact I’ve found that in most situations it just gets you killed faster). Playing defensively made the game possible for me and most bosses absolutely allow for it. There are only a few where you are made to feel like you’re constantly in a scramble, and depending on play style and ability, are either the best or worst encounters in the game as a result.
Additionally, as for building up stun, this is rarely if ever relevant in most fights. Gascoigne is one of the few fights where I found it to be consistently relevant, but most other bosses have durability that is so high that I was surprised when it happened rather than expecting it. Again, since there’s not a consistent way to know when you’re going to stagger them, it’s less helpful and more disruptive to a fight when the pacing suddenly gets interrupted. The only way I could “know” when I was going to stagger was when I was using weapons that nigh-guaranteed it, such as Kirkhammer charges (and then it’s really disruptive when you don’t get the stun because you learn to expect it).
There are very few fights as aggressive as Gascoigne, and while there are a few more in the DLC, scramble fights are the exception, not the rule.
Not including Chalice dungeons, in the base game I see three as scramble bosses (BSB, Gascoigne, and Gehrman). DLC I see Maria, and Orphan of Kos. I haven’t actually fought all of the bosses in the Chalice dungeons, looking at the list, but of the ones I’ve fought I’d still say scramble bosses are not common.
Also, just an experiential factoid - I remember people talking about how difficult Flamelurker was in Demon’s Souls, but found that using my shield was a good way to handle the frequent slams. Additionally, they had enough regularity and consistency in motion that I always felt like I could plan for them. Gascoigne reminds me very distinctly of Flamelurker but I think that’s also why the fight feels so different. Without a shield, it’s difficult to feel like you’re actually prepared for the attacks. You can know they’re coming, but because there’s not a guaranteed way of mitigating them (i.e. tracking can still sometimes get you even if you think you dodged at the right time), the fight takes on a very different tone, and feels like you have to handle constantly being rushed down. And yeah, I’m not very good at dealing with those sort of in-your-face situations. Probably why I’m also not very good at fighting games. I want to slow the pace of the fight down and play a zoned, control heavy game, but most matches tend to get decided on the scramble and how you play in those situations, and I don’t think I perform well in those situations.