The design is bad if the cost of having shorter rounds is making the success of the level inconsistent based purely on RNG. If you want a redirect that last more than 2 turns, it'll be more consistent to use a Royal Huntsman or BK Tristan.
To answer your first question, I did quit a certain game because of the RNG Violent procs (similar to refresh in this game) that were not strategic to the point of being forced to use it everywhere just because there's no strategic alternatives. It's not as bad now because that game listened to player feedback and actually worked to re-balance the violent RNG (1 activation limitations in PVP, made it diminishing chance to activate outside of PVP). That allowed players to once again build strategies rather than relying purely on coin flips.
This is not just a gripe but a serious concern to the possible direction of this game. I do enjoy VF and that's why I'm hoping that VF will learn from other more developed games so that it will not make the same mistakes that it's predecessors did.
Well I have been mentioning that problem for some time, but got no positive replies (or any, regarding that), which led me to believe that it's a problem that only I see (and hence, a personal gripe). I've addressed that multiple times so I wont do it again here.
I still believe that certain quantities of RNG are needed to keep a game fun. However, it is unhealthy for a game to be overly reliant on RNG and wouldn't like VF to go in that direction. Usually adding more RNG takes away from the strategic aspects in games.
With this RNG on spawn mechanic, the devs have raised the bar of a stage's potential difficulty. They could make it so you need 4 other non-cleanse non-taunt units in your team plus one HD Arthur to play both cleansing and redirect roles. Since "you cannot rely on it", it would then essentially force players to restart the game and hope it procs. The upper limit of this RNG on spawn mechanic will lead to units either being useful or useless based on turn-1 coin flips which contradicts this being a strategy based game.
Putting aside the upper-limit point for awhile; On your point about adapting to the coin flips, i agree that there are few ways currently in the game to adapt to this for Arthur's case. However, for these turn-1 on-spawn RNG mechanics, you are limited by the 5 unit team limit if you plan to use him for his RNG on-spawn redirect. Having to bring backup plan unit in your team essentially takes up one or two more slots in your formation just in case RNG fails on turn 1.
Back to the upper-limit point. Before these RNG on-spawn mechanic was introduced, generally, you fail a run due to your units and equips not being developed enough or you had to change your team composition/strategy. Now it can be a coinflip that decides if you win or lose especially when you think in terms of the upper-limit difficulty i mentioned.
Arthur Paladin is on the opposite end of this RNG on-spawn activation mechanic as HD Arthur would be OP if it was 100% activation but Paladin Arthur is underwhelming without 100% activation.
I agree. Too much RNG is definitely unhealthy to the game. However, it does not mean that RNG will serve no strategic value, or take away from it. (I say that as a player of XCOM)
The ability to restart to try to reroll is a issue of itself. It can probably be fixed somehow by using RNG seeds for battle, but idk how they coded it.
If you need to rely on the coinflip to win you the battle, it does mean that you are either a really bad commander, you do not have a good fallback, or you are undergeared. (You, as in the player). If you do not have a good fallback, it's your choice to rely on RNG. If you are undergeared, it's good that you even have a chance to win, and again, it's your choice to rely on the RNG.
That being said, I can't even think of any good fallbacks to rely on if Authur doesnt proc in stage 1 turn 1 lol.
In fact I would say that HD Authur isnt actually OP. He is right on the curve as an RNG based unit. When his ability procs, he's above the curve. Not by an insane amount, since you only get 2 turns, but quite above. And, according to your wording, when he doesn't proc, he's below the curve. (I feel that he's not as bad as you say even without his on-spawn effect tho). Which is a good position for an RNG based unit...
Again, I'm ignoring the fact that you can restart to reroll the proc because it is an abuse rather than an intended mechanic. They DO HAVE to fix it, though, or the RNG would, of course, serve no purpose.
I feel that the units would overall be better if they can reproc their on-spawn effects with their skills... but that'll make HD Authur a little OP? Maybe tweak something? It's really annoying to me that their on-spawn effects become irrelevant after 2 turns.