In 3.18 there was a HUGE difference between sedimentary and other biomes in terms of the viability of iron production.
In 3.19, it matters enormously where you embark. Some sites have loads of metal, others none.
What about things that aren't iron? In .18 you would get a good spread of metals and stones on a site because everything that could appear in a layer stone had enough opportunities to do so.
In .19 you get lots and lots of very few types of metals. As a test I embarked on an area that had, between its three biomes, at least three shallow and three deep metals plus flux. The result was five different types of ore, three of which don't do anything that stone and wood can't do. If the embark finder lists the presence of metals without listing any stone types, there should be some meaning to the information beyond 'small chance of something useful'. Had one of the metals turned out to be iron ore, that would have been good for a weapons industry. But the central problem would still have remained. There's not enough mineral variety underground. Iron and steel are good and all*, but the geology of an embark should hold some interest. Once you've figured out which few gems and non-layer stones you have on-site, there's no point in digging around for goodies.
Maybe this will be less annoying when the trading changes are done, but that's a quality of your civ and neighbours and not the embark itself. I think the real problem is that the only ores that really do anything are the weapon ores. If you could use lead in glassmaking, or use specific metals in a way that has an impact on manufacturing beyond changing the material something is made out of, then they'd have a place in the site finder. As it is you might as well ignore whatever the map tells you about mineral composition as long as it isn't 'no metal anywhere'.
*Well-trained dwarves in leather and bone are still pretty good at taking on marksgobbos in a frontal assault. Give the enemy something to charge at and then drop down behind them, and there'll be even fewer chances for them to make meaningful attacks.
Is there a way to get water from a cavern that can't be used as a shortcut into your fort by a flying/swimming/building-destroying FB?
Just an idea: Have a pump between cavern and reservoir, and fill the path between reservoir and pump with multiple fortifications. Things can be pushed through fortifications if there's flow, but if something destroys the only source of flow en route to the fortifications then it can't be pushed through.