it's still damn near verty difficult to say, solo a nightfall.
I think the game is pretty hardf.
The safe areas should be between encounters, not fail proof areas that you just need to locate in order to beat the bosses in hard mode. Omnigul, get to the back of the room, there is a small room above the ground, 2 men can stand there, one is a dedicated reser, the other provides DPS for the boss, not a single mob can reach you. Nexus, 2 jumps and you are above every mob, DPS the boss until it dies. The priest had it's cheese spot, the one left is not as easy, but again, the idea is to get above the mobs, and cycle with a location that is impossible to reach for mobs. Tarus, stand behind crates, mobs cant reach you. Phogoth, stay in the entrance room, DPS the boss via a very small window. Bungie knows about the last one, they made a shriker appear if you stand in the original cheese room. And again, not a single mob will get to you. The biggest challenge is usually Ammo runs because not everyone has a IceBreaker.
At some places i think it's a flaw in the way they made the game, it is like some zones a mob free because they serve as a link between the different parts of the map that is loaded in, oh well it is a PS3/360 game afterall
Well, something like a nightfall strike (with burn) solo is ridiculously hard, regardless of cheese spots (which basically only apply to bosses). Things only get (sort of) easy if you group up. But yes, it's rare to die even in a nightfall with more than one player. The ability to res each other is just too OP. But worth noting, they specifically dumbed down group difficulty in that patch.
The Raid is definitely challenging if you play it legit. And the Crota cheese is not a safe spot, and I'm not aware of many safe spots in Crota's End. The cheeses are more like exploits, often of the Warlock's self res, which must be causing Bungie problems with all it's bug causing abilities.
So yeah, the difficulty is a vast gulf between group and solo. I rarely die (meaning the whole party) in a group, but solo is difficult in nightfall and now even weekly or daily at times, regardless of cheese. So if you want a challenge, simply go solo.
It's also gotten more difficult with recent patches and expansion. I used to solo all (except raid of course). Nightfall's were very difficult but doable. Now it's basically nightfall's impossible to solo, and even weekly's are borderline, and I even got stuck on a daily 30 last week. Of course some depends on how much time you feel like spending on any task.
Also I'm still skeptical of your nexus cheese spot. Those spots do not protect you from all damage, when I have tried them. Have you tried actually using this spot to solo it at a 30 or above or in a nightfall? I dont think it would work. Besides that if you dont get there the first time you are dead.
Difficulty, you can look at it another way, the bosses are overpowered, thus you cant really fight them legitimately at highest levels of difficulty.
Is this a flaw? I dont know.
The whole game's difficulty is an interesting question, part of me would like all game content to be easy if you max out your level and weapons all the way, in other words grind your way to the top, and then the game is your playground. Then of course the next expansion would make things difficult again in this scenario, until you master it as well. It's not really that way, some things are always still tough even if you were 32 with all the best 331 weapons. I guess they want there to always be a challenge, otherwise you would risk players getting bored. It's a catch 22 in that way.