Sure they were powerful. They killed Corran's grandfather (the un-aptly named Keiran Halcyon), and fought against Jedi Knights of the Old Republic. That has got to be pretty tough. And they seem to be Dark-Siders to me.
Oh, those guys were powerful enough. They made an even match for a group of battle harened Jedi Masters. It was only a limited fight though, no more than a half dozen people of each side. And all of those guys were all deep in the dark side. They were all on the other hand, killed in the fight. Th current Jenisaari were there students and were not as powerful or knowledgable. Plus they produced a bizzare hybrid of Jedi and Sith philosphy.
PS. Corran's grandfather was Nejaa Halcyon not Keiran. That was Corran's alias at the Jedi academy.
Are you seriously saying that the Jensaari could not have overpowered Tavira and her guards, even in the considerable numbers that they were in? They could have removed the threat of her little armada quickly and relatively easily, IMHO
That's exactly what I'm saying. There aren't that many of them, certainly not more than 100. And not even all of them were fully trained. A half trained kid isn't much use in battle. Plus, Tavira took precautions to prevent a sufficient force from getting at her. Notice she never lets more than one or two around. Plus, she simply has to ry the planet in orbit, one or two warriors might kill Tavira but at the cost of their wold dying.
Also, in some ways their training seems to have exceeded even the training of the Jedi. Remember that they were able to construct both their lightsabers and their armor. Even Jedi Masters sometimes have difficulty crafting just lightsabers, and it was implied that making that armor was actually more difficult.
They certainly seem to have a lot of martial training. They can fight well enough against normal people but they aren't ny where near Jedi level. They don't have the combat-precog skills of a Jedi. Remember Luke and Corran kicked the asses of seven of their better (if not best) warriors with only a little trouble. They don't have the edge to overpower a ship full of blood thirsty troops. Not even close.
The skills involved in creating lightsaber are master level skills. The jedi have however ritualized it so that a Knight can do it. After all Corran, who i most emphatically not a Jedi Master, was able to. Where does it say Jedi Master's were not able to make ligtsabers?
The armor was supposed to a superb piece of craftsmanship and a work of art but nothing really force related.