Yeah I'm not a fan of putting Myler back in at HB either. For me we have 2 sides running alternately for the remainder of the season pretty much, and Walker is FB in one side and Myler the other. I want players playing IN position where we can, and if Myler was only going to play half at Leeds I'd have let him go, personally.
There is an argument to bring in Holroyd, Smith and Walker against Saints - in the hope those boys are a) fresh and b) want to prove a point. It also tells them that they very much are in "the plan", which they may need to be signalled now I don't know. The Saints game is a big one for me: win it and we might have a tilt at the grand final, lose it and it looks very difficult. It's almost like an early eliminator (for us!).
As I've said before though, the problem with swapping Myler and Walker is they're just very different players, and the rest of the team has to adapt.
I do see what people are saying about the tactics of throwing Saints and focusing on the more "winnable" games.
The other side of this is that Saints have had 2 weeks so are fresh yes - but that weekly intensity can sometimes be a benefit. We've seen this in Grand Finals before...