Lets break this down, mathematically, for those who follow pure conjecture rather than facts.
Going with "stock" or "base" models here for comparison purposes.
Lets look at their damage.
Rose:
9 dmg per thistle
20 thistles
Takes 4.5 seconds to unload her entire magazine
For 180 dmg in 4.5 seconds
Engineer:
20 base dmg per hit (35 for a well aimed head shot)
12 rounds
Takes 11 seconds to fully unload his clip
That's 240 dmg over 11 seconds for body shots, or 420 for head shots in the very unlikely chance that every shot is a head shot.
99 seconds is the first amount of time where Rose's clip time, and the Engineers clip time meets at the exact same time.
In 99 seconds, Rose can unload 22 entire clips, the Engineer 9. That breaks down to....
3960 dmg for Rose
2160 dmg for the Engineer on regular shots, or 3780 damage for head shots.
That breaks down into Damage Per Second (DPS) as this
Rose: 40 DPS
Engineer: 21.81 or 38.18
That's raw dmg for the base class, and since that's what you were complaining about, that's what I addressed, mathematically.
Again, that's MATH, free of opinion.