The Tavern

I would really like an option to have a higher chance of unique monsters and/or random portals. (Currently you see less than 30% of them in average game).

I think one issue with this is that unique monsters and portals are overall pretty dangerous. If the devs did this Crawl would get significantly harder in most cases and characters ahead of the power curve would have an even easier time. I'd like to see more, not less, regression to the mean in Crawl, but maybe that's just me.

A hundred times this, as the kids say.

Timed portal vaults are arguably the biggest cause of power spiral in DCSS. Strong characters get stronger from all the extra xp and loot in the portal vault. Characters too weak to do the portal vault (or that can't reach it) stay the same. If your character can't do all of a dungeon level, you can just come back later and get all the same xp and loot as a character that did all of the level right away. If your character can't do all of a portal vault, it's permanently weakened.

Power spiral is always a problem in games where you prohibit backtracking, and usually prohibiting backtracking is worth that cost...but prohibiting backtracking in 1% of the game is not much better than 0% at all. Portal vaults are still sufficiently unique and interesting to justify their existence (except labyrinths obviously), but generating them more often would just hurt balance and not help anything else.

For normal people, part of what makes crawl fun -- rather than a Go-like ultimate test of pure skill -- is that some runs will be easier than others thanks to randomness. So it's OK that sometimes you will get a big boost from a couple portal vaults.

This is true. Sometimes randomly getting very strong is a big part of what makes roguelikes popular, it scratches a skinner-box esque itch. There's always(or often) a feeling you could find something awesome that makes you really powerful, and for a lot of people, that is the main draw.

And I posit that the chance of finding said awesome item(s) shouldn't be made higher for characters that are already really powerful. Yet this is what portal vaults do. So I don't want the effect of portal vaults to be even bigger.

I like high variance in what items and monsters generate, I'd like there to be more randomness in fact. But I don't like power spiral, which is completely unrelated to randomness.

And what if timers were removed?

Then the portal aspect of them would be rather pointless; you'd be better off making them regular vaults at that point.