Just to answer my own question, I was wrong. The multiplier you see is the only multiplier you get. So, in the example, I gave, a critical hit would only do 150 damage, not 250. Not as good as I originally thought, but with a lot of effects that trigger with critical hits, critical chance is still a good option to invest in.
When crafting, 1.5% crit costs as much as 2% attack. With base crit damage, 1.5% crit only increases damage output by 0.6%, while 2% attack increases the output by 2%. Now, while it's true that crit is more useful than just damage output due to certain abilities that trigger on crit, there will be a point when those abilities can be kept with near 100% uptime on a target (or between internal cooldowns).
For example, a 2H sword has an attack speed of 1.125/s (DPS/dmg per hit). The ability "Shield Breaker" reduces target armor by 20% for 6 secs on crit. In 6 secs, a 2H sword can hit a single target 6.75 times using basic attack. The probability of scoring at least one crit hit every 6 seconds on a single target is as follows:

As shown, starting from 30% the effectiveness of crit % for triggering the ability starts suffering from diminishing return. It's also worth noting that this is based on the assumption of attacking only a single target using only basic attacks. Even a single extra enemy, or use of fast hitting abilities would drastically reduce the amount of crit % required to keep up the proc ability most of the time. Sure, around 15% crit may be very nice. However, the higher it goes the less useful crit becomes. On some highend store bought weapons, the crit % given by the weapon is already quite high.