How would you weigh it against other RPG ?
Me? Hard to say at this point. Certainly the most frustration I've had from an RPG, though I also see there are plenty of merits in the design. In fact, the combat feels quite awesome when I'm not stuck somewhere, or hearing the critical condition music every 5 minutes.
I have to say though, in general, I like games to be easier. The thing I miss most in console gaming now is a cheat device which I can use to get out of tight spots.
For some RPG, the varied possibilities in fights are mainly about the equipments, a few stats and matching elemental/physical properties of attack and defense, e.g. Fallout 3. For the more conventional JRPG I played such as WKC, FF12 and before, it may also concern some specialization, who learn what magic etc. Once you've set up these basics, what happens in battle are mostly quite predictable. You may not know the weakness of an enemy the first time you see it, but I'd say it's mostly straightforward decisions if you already know the enemies.
Resonance of Fate has those elements that you need to prepare but is far more varied comes the time of battle. The way a battle plays out is more unpredictable even with the same stats and equipments. By that, I don't mean unpredictability coming from a random number generator. It's how various small things can interact to make a big difference that's hard to foresee in advance. It's probably not entirely by design either. In the Neogaf official thread, someone posted some funny photos about a fight that made him suffer long and hard. It turns out to be extremely easy for the way I play. I simply stood still and only use basic attack from the starting position. I don't think stats or equipments are the crucial difference in this example. I think it's just me not moving, not triggering the big hitting enemy's move towards me and hence the cascading effects that would follow.
Small things like moving a character forward a bit can also affect AI's targeting in general and affect who takes damage, how much uninterrupted time another character can have to charge up an attack etc. Attacks of sufficient strength can stop action in this game. Who charge up a bit faster to stop who, how long to charge up for it to be enough to stop an enemy's attack, the relation between target distance and charge speed etc. all combine to make battles less straightforward than other games. On top of that, the HP (& Hero Action) management pile on another layer of risk. Without going into details, I'd say the HP management is like keeping a ball on the peak of a dome. You try to keep it center and it may seem ok for a while, but then an unexpected jerk and now you watch in horror as it goes downhill at an increasing rate, taunting you all the confidence and comfort a moment ago was totally misplaced. The game is designed with positive feedback loops to stamp on your balls when you're down.
The way turn-based and simultaneous actions are blended together draws comparison with Valkyria Chronicles. I played the Japanese version of VC and don't understand some of the special effects, but I can say the combat of RoF and VC are very different experiences. They don't just differ in scale and length. Other than some scripted events, in VC, you carefully play it step by step and you'll win your battle in due course. It doesn't work like that in RoF.
The talks about difficulty also invite comparison with Demons Souls. I'm quite sure I died far fewer times in that game than I'd end up in RoF. I played DS cautiously, mostly keeping my distance from enemies and that served me well throughout. I'm as yet unaware of any approach that can work so well throughout RoF. Anyway, as I mentioned previously, I think my frustration in RoF may have more to do with the way I die rather than how often I die or intrinsic difficulty of the task.
Having said all that, when I rate/remember an RPG, I mostly think about the story and I'm less than half way through this game. My favourite RPG remains Xenogears. If you also count Folklore as an RPG, then that would be joint top in my mind (despite feeling it's too hard in a few places).