I just tried a fortress in .19.
I have to say there is definitely not enough metal.
I've only played .18 so I might be biased a little; but average metal quantity should be upped; even with a caravan arc starting.
First of all, having civilisation withought ANY access to metal already rules the current setting as not viable.
Then comes the concept of realism. Compared to real life, .19 maybe doesn't require to have ores more available, but really I doubt it means that it can't (actually, screw that; you KNOW there aught to be more ores if you dig down to hell itself.)
Then comes balance and the rule of fun. From my experience it seems that there is both little ore variety and quantity, or an outright huge amount of 1 type of ore (relatively speaking; might still be less than in .18). Now the concept of "getting metal from caravans" is fine, but entailing it to also mean being 100% dependant on caravans is a big no just from a balance point of view.
Furthermore, we are dwarves. Dwarves cut trees, dig down to magma, mine ore, play with magma and make metal stuff: that's what we do. Rule of fun states we should be able to do it with if we want to. Having no ore is an immediate impediment. The absence of metal on an embark or civilisation is reasonable if it occurs MUCH less frequently than a reasonable presence of metal on those embarks/civilisation.
That being said, .18 ore are a little too varied for both balance and rule of fun. If I had been an experienced player during 0.18, I would had advocated a small reduction of ore variety available on an embark, even if it requires an increase in quantity.
Ore quantity is in my opinion less of an issue, especially regarding rule of fun; knowing you have a finite amount and having to make do with it is important; but since you can melt the whole thing anyways and do something else, I think quantity should be used as an upper limit to discourage and avoid utter cheating rather than a component of carefull management.
I however am in favor or oreless/nearly oreless embarks, but I think they have a more "accidental" chance of occuring; like making up around 10% of the world map and distributes in a random fashion, so that if a player actually looks for it, he can find it; and if you embark at random, you have a chance ending up with no ores available to spice things up.
tl;dr
Need more different ores embarks, not to the point of 0.18 because that ruins the fun, but enough to let the player do thing with metal if he wants to and not be forced to rely on a caravan if he wants to do a reasonable project.
Keep around 10% of worldgen oreless, including a civ from time to time, so that you can end up on a metal-less embark and have to find ways around it.