Some Gems just have too many restrictions/penalties for what they do

In general I would say that some gems go overboard with consuming ailments/making spell unable to inflict ailments.

There are situations where the gem would definitely be too powerful if it didn't have those restrictions. But let's look at Flamepierce.

Flamepierce makes projectiles pierce on ignited targets. There is a pierce gem that can make the projectiles pierce on every target. However, Pierce will remove 10% of damage after piercing. So in theory you could use flamepierce to pierce targets without losing damage. In practice, you are dependant on first making sure everyone is ignited. And that's a very complex precondition to match, it will definitely need you to invest a huge portion of your build on adding ignites before sending the projectile. But I think it's a nice trade off. And when Flamepierce can do more damage than Pierce, it's cool.

However, Flamepierce also comes with a restriction that makes the spell unable to ignite. This one really limits the whole deal. And I don think it's not very necessary . Again, in order to be able to do more damage than with Pierce, you need a lot of setup that Pierce doesn't need.

I've experienced similar problems with trying to make Elemental Discharge to work. It can greatly limit your spell, it won't be able to inflict any ailments and it will consu,e ailments as well. On top of all that, there's a 1 second cooldown.

if you think this is restricted, take a look at Syzygi support.

It needs: mob being on fire, fully broken armor, then the supported skill needs to be the one that stuns the mob, and that skill needs to be a slam that uses a mace.

Sure perma intimidate is great, but this is no longer an rpg, its a jigsaw puzzle. I would even say that most skills currently operate on the 'guess what the dev wanted you to use it with' basis.