I myself really enjoy using Saga, but they are different than other Vanguards, so I wouldn’t suggest bringing them to every stage.
One of my first Operators promoted to Elite 2 was Courier, and I still have yet to regret it. They generate sufficient DP for most levels, while being very tanky, especially for a Vanguard. I usually pair them with a more offensive Vanguards, such as Texas or Saga.
But, if you really need DP, I would use Elysium if you have them, overwise Myrtle is a good option.
However, you have Saileach. Saileach is an excellent buffer, and can do some damage if needed. Are they replacement for anybody? No, they don’t generate DP as well as Myrtle of Elysium. They don’t last long like Courier, or even have two block. BUT, they are best Vanguard at buffing others AND generates good amounts of DP.
So my suggestion, based on my experiences alone, would be to continue bringing Texas to every stage, promote Courier to Elite 2, upgrade Elysium or Myrtle aftewards if possible, and get Saileach to Elite 2.
An honorable mention would be Beanstalk, but I’ll leave that for someone else to explain…
There’s no such thing as too many Vanguards, right?