Zinogre was harder before? Well, damn, maybe I'm just too bad at the game, because while the thing doesn't trash me too hard, it's not a comfortable fight, either. It feels as if it was always on the attack, especially when it goes Super Saiyan, making it very hard to catch it. 

Bishaten is very original and its sure is a fun fight, but its one of the easier monsters, hardly a challenge. So I cant really rank him too high. Maybe it does deserve to be in B tier just for the enjoyability. 

It was harder only in MHW, because it was added as an endgame monster in that game. It was even more agressive. Its usual dificulty its like in this game. 
Overall its one of my fav. monsters in any entry. 

High rank is less punishing than I expected, though I am definitely not complaining. Should finish up the rest of the 4 star tier tonight. 

I wonder whether the updates will just add 8 star and 9 star tiers of super hard endgame monsters, or some others as well.

Fair enough, for me I don't mind if a monster's not too hard so long as it's fun to fight and a cool design. 

Just a personal opinion but I find Tigrex more difficult than Magnalomo

Eh, I think Zinogre, while still not too challenging, is actually still one of the harder monsters in the game if you do him solo. I feel like if I'm to solo monsters in the highest rank, the only ones that put up a challenge are Diablos, Nargacuga, Goss, the final boss (because I've fought it very little), and to an extent Zinogre given how it can punish the player if they aren't careful (which is how I play most of the time lol). However if you're doing multiple players at once, then the only one that is really hard is Nargacuga, and maybe the final boss (Diablos might actually count here too).

For me, by far the hardest is Nargacuga though. Which is a little weird given how I always heard he was one of the lower tier flagships. He feels like the only one who can actually kind of match a 4 man team, given his quick swipes and constant moving around, as well as his compact-but-still-large size, means he's always bound to hit someone usually.

In general, I think the biggest problem this game has, and something they'll probably address in the expansion, is that while monsters certainly do a lot more damage than they did in base World (at least from what I remember, base World was very unpunishing, and this is a welcome change), monsters in multiplayer don't seem to account very well for how much stun multiple players might inflict at any given moment. About half the match in any multiplayer game becomes ping-ponging the monster from one stun animation to the next. Hopefully the elders in the update don't suffer from this.

Oh yea: Rakna-Kadaki is way too easy.

It's actually kind of funny that he's the reveal for the highest rank. Honestly would probably make more sense if Rakna was the village introduction and Goss Harag was the HR7 introduction xD Given Goss Harag in HR can be challenging at times

I dont really think any one of them is particularly challenging tbh. Even in HR the difficulty is pretty much dialed back.
I assume the difficulty spike will come later, when they update the game and start adding Elder Dragons.

For me the hardest fights so far are Nargacuga, Almudron, and Magnomalo. 

That said, I have yet to reach Rakna Kadaki, Rajang, or either of the Elder Dragons.

I hope some of the DLC monsters are Village Quests or at least not only super-hard endgame ones.

I can't stop calling Nargacuga Nicaragua, or Narcagua, but I agree that it is one of the most problematic monsters (still have to fight the remaining 6 star village monsters, though), but I insist is not as bad as Zinogre. Perhaps I have gone with that impression because I farmed Zinogre for a while for its plate (to no avail, btw).

Question: could it be considered acceptable to kill, say, Magnamalo and Rathalos in a single solo quest in about 25-30 minutes? I spend the first 5 minutes completing subquests as quickly as possible, the remaining time is me killing the mobs. I feel like I'm lagging behind, as if wasn't putting the amount of skill was demanding out of me at this point, because, while it's not super hard and I haven't failed a quest a single time, it's still challenging, a little bit too much, I find myself taking potions and using healing bugs very frequently. I have watched a few videos of people soloing big monsters with the gunlance (there aren't many, really), but I can't replicate the ease with which they kill the monsters, they are just too agile, which is the main problem. Tomorrow I'll explore other weapon, I think it's time.

Yeah Zinogre is an arsehole, I think the only reason I don't rank him among the hardest fights is that I fought him before in 3 Ultimate and 4 and he was even harder there.

25-30 minutes for a solo run is fine. Though if you are struggling with a Monster, changing weapon classes can be a good way to get unstuck. I struggled with the gunlance against Almudron but he became a lot more manageable when I switched to SnS.