First

CR 1/4 barely 1/2 at best. 

Throw a dagger at someone and then stop them attacking you back? Sounds like CR 1 to me.

That's not how CR is calculated there is a DCR and a OCR. Neither of which average much more than 1/4 CR. 

They're changing how CR is calculated so that it's more reliable and scalable. For example, the new Animal Lords are CR 20. Normally, that would indicate a party of four level 20 characters would be a good match, however, three Animal Lords would be a high difficulty encounter for four level 20 characters. One Animal lord is a high difficulty encounter for four level 14 characters.

Quote from Soggy2002 >>

They're changing how CR is calculated so that it's more reliable and scalable. For example, the new Animal Lords are CR 20. Normally, that would indicate a party of four level 20 characters would be a good match, however, three Animal Lords would be a high difficulty encounter for four level 20 characters. One Animal lord is a high difficulty encounter for four level 14 characters.

 Ok, sounds good. Do you know where this information about this can be found? The issue is that these stats as they are ( I know they are possibly beta, but rarely has WoTC ever changed something they even Beta publish) are easily defeated by a party of designed level according to the DMG.24. 

As currently statted a party of 4 level 4 PCs should be able to handle 5 of these CR 1's as a low encounter. The encounter doesn't last more than 2 rounds and the PCs will loose less then 20% resources if even that. Good encounters last 5-6 rounds becasue many spells and combinations take a round or two to set up. Using the 2014 monster building rules 5 CR 1's would have nearly twice as many hitpoints and for sure eat up 20% of the PC's resources. 

For Animal Lords and their CR, the Dungeon Dudes released a video a couple of days ago.

I don't know how lower CRs are calculated, only the one revealed by the Dungeon Dudes. Personally, I'd add in a few bandits and maybe add in the CR 6 Pirate Captain. Generally, I want my players to win, so I'm not too bothered if they take out enemies in a scant few rounds. A lot of players like a good power fantasy, and hitting pirates until they stop moving is just that.

On another side, these pirates could be running the ship that the party has rented for a quick sea adventure. Sahuagin attack as Sahuagin do and you need a quick pirate stat block. There's a whole variety of ways I could see that playing out.

What is a pirate's favorite letter?

c

Nay, ye think it be C, but 'tis the ARRRRR!

Also defensive and offensive CR have never been the only consideration. Special abilities like being able to charm someone would raise their effect defensive CR because it's a defensive ability. But yes this is kinda weak for CR 1, especially since the charm is mid DC, one turn, and doesn't stop you from attacking one of their allies instead.

"Good encounters last 5-6 rounds becasue many spells and combinations take a round or two to set up. Using the 2014 monster building rules 5 CR 1's would have nearly twice as many hitpoints and for sure eat up 20% of the PC's resources."
That's not how it works out in practice. Very few creatures earn their CR off of defensive CR, most CR 1s having around 21-44 hp. 
And and encounter against 5 glorified bandits isn't going to be a tough or long-lasting battle. 
These guys can however use thrown daggers to target your more fragile members, use enthralling panache on a barb or fighter in a pinch when injured. 
They have reasonable AC and proficiency in Dex & Cha saves, and initiative.
5 against a party of 4 level 4s is both a minor challenge, and a small chance of a party wipe.

Cr 1/4?! If you put a lvl 1 pc  in a 1v1 against that, they will get destroyed, except if your players brought powerbuilding to a whole new level.

Pretty good stat block

Enthralling panache feels weird. Like, narratively how do you describe that working? It's not magic, is it just that it's so amazing of an acrobatic display that your charmed by it?

Quote from IamLousy >>

Enthralling panache feels weird. Like, narratively how do you describe that working? It's not magic, is it just that it's so amazing of an acrobatic display that your charmed by it?

This is my exact problem. I don't mind harder stat blocks, but logically why is this pirate able to charm infinitely...?