Are easier tactics better for improving tactical vision?

Firstly, I would like to define "easier tactics" as tactics that are not entirely obvious, but simple enough to figure out in around 1 minute. I've heard the term blitz tactics used to describe them, and you are graded based on how quickly you solve the tactic.

Pros of doing timed, but easier tactics

• Improved pattern recognition
  • Repetition is key. Since you are doing more tactics, you become more familiar with these tactical ideas.
• Able to spot solutions quickly
  • Since you are being timed, you are always alert. This alertness may translate over to games.
• Keeps you thinking
  • These puzzles are easy enough that you will always have an idea as to what the solution is, so even if you are unfamiliar with the puzzle, you won't give up as easily.

Cons of doing timed, easier tactics 

• More likely to plateau. 
  • Since the puzzles are likely similar to puzzles you have seen before, you likely won't be exposed to harder puzzles. This will potentially cause you to improve slower, and even plateau. 
• More likely to become careless
  • When doing harder tactics, you always want to be absolutely sure that your answer is correct, or else your efforts will be for nothing. By doing timed, easier tactics, you are more likely to take a wild guess, instead of fully understanding the position.

Perhaps the answer doesn't even matter, or it could simply be in the middle. I simply want to get opinions from other people so I can better understand how to balance the difficulty of the puzzles that I do. Thanks.