I've tried the "hold L2 throughout the battle" and that wasn't effective. Warping out to regain my composure isn't helpful or fun if I can't warp back in and even as admitted in the advice comments, it's hard to telegraph moves and they come from unseen directions.
So what is the strategy? Just hang out at the outskirts of the battle and poke at the closest enemy? Hardly seems fun and ideal, especially with an iron giant and other monsters abound.
Edit: I seem whiney, but I'm genuinely curious if I'm missing something. I've only just seen tips on some kind of chain link attack or something and I'm not sure how to pull that off and I remember something about armiger attacks with L1 and R1 but I don't remember the logistics. Taking a break was a bad idea and I'm guessing using these would be more helpful to me than just standard attacks and phasing. Or some other form of defense?
Apologies. After my last post I went home and went to sleep. I'm back now.
The situation you described in your second paragraph with the Magitek soldiers, Iron Giants, and other monsters sounds like you were out at night and got overwhelmed. (which is kinda the point of monsters at night.)
In situations like that magic greatly helps clear some of the smaller monsters. As for the big ones you want to frequently use Techniques and Armiger. Techniques will give you a lot of invincibility-frames while the camera is on the other character and is generally helpful.
With the dual-bladed Magitek Soldiers you want to be on the defensive most of the time with them. After they attack they will have a second or two of being open for attack and that is when you go on the offensive and try to stun them with an end of a combo. (You can force the end of a combo by attacking twice pause for half a second and resume attack. This will cause a big final "end of combo" hit and usually stuns Magitek Soldiers and has them knocked to the ground.)
There is a variety of ways you can go about it really. But unless you want to same healing items, the best strategy to go with is stay on the defensive and make liberal use of windows, Techniques, and Armiger.
Leading up to release, and especially with that Omen trailer and Kingsglaive, I was excited about learning of Noctis' family's dark secret ties to the astrals and maybe find out they were born of/part of Diabolos etc etc. But the game skimped on their dark motif for the most part and was more of a rich kids lost in the back country just as confused as everyone else.
It'd be nice if they added in more lore and history and it not being left to confusing pre-chapter cutscenes and small paragraphs from a book.
Edit: Granted I'm only at the beginning of ch. 9 but I've kept up with the leaks/spoilers pre-release as well so I know What the game is and isn't generally speaking.
The Bestiary helps greatly with this now.