@caitsith
There kinda was. (Indication of power difference, to be exact)
The older sister of Noire was incredibly surprised when the mother said Yuna might be a C-class or higher, and Noire' sister is the strongest student in the most prestigious school in the nation. This likely indicates the gap in power between classes may be larger than most fantasy stories that utilize this 'ranking' structure.
When the black viper (a b-class) was announced everyone went into a panic, and we do see why- it's insanely big, powerful, agile, and durable. However, Yuna defeated it without breaking a sweat, meaning she's handily above B- class, meaning it's not too much of a stretch to say she is easily A- class or S-class.
When the guild leader said a A-class (not even S-class) killed all 10,000 monsters, no one doubted her and even mentioned that they could destroy mountains with a swing of the sword( a feat more impressive than anything we saw Yuna do at this point, by the way). This means the power structure and scale of this world is truly exponential as you go up the ranks. The fact that the Guild thought it was appropriate to peg her feat at A-class means that as impressive as it was, it
still wasn't enough to be considered S-class.
Lastly, and most importantly, in the very first chapter Yuna mentions the suit's buffs that scale off her level make her insanely broken
for a MAX level character like hers. However, when she was sent to this world she was sent back to
level 1. She was able to easily defeat 40 wolves and multiple D-rank adventurers at that point. And because of how exp scaling works, she would be leveling up incredibly fast since she's a low level, meaning that this chapter, she's likely several dozen times stronger than when she arrives, and will only continue to get stronger until she hits the level cap.
Now, as for the actual upper limits (when she finally be comes MAX level)- I dunno, it's entirely possible she may be a God in that world since, ya know,
actual God gave her the outfit and sent her here.