I'll assume that “time saving strategies” refers to skipping packs by various means. The value of skips varies from dungeon to dungeon. In
Halls of Valor, e.g., there really aren't any skips that are impactful -- it's just a question of which packs you want to pull. In other dungeons like
Eye of Azshara, the ability to skip straight to
Король Волнобород by using the boat shaves minutes off the dungeon and has become so ubiquitous that people don't even know how to do the dungeon anymore without using the skip.
There are a few ways to skip things and the methods used range from “completely legit” to “ok everyone turn off your streams for the next 30 seconds”. If you skip trash packs by having your tank pull a pack off to the side while your group runs by, there's absolutely nothing sketchy about that. It can be hard to determine how Blizzard intended that dungeons be run but the fact that mob count exists and that you can finish mob count without pulling literally everything in the dungeon means that Blizzard expects you to avoid some trash packs entirely. It's the same deal with
Скрывающий покров or using
Притвориться мертвым to reset a trash pack -- those abilities were obviously designed to avoid enemies.
Intentionally dying and having your healer mass res you starts to get a little grayer. It's a very common tactic and I think most people would say that it falls under “intended uses of mass res” but I could certainly understand how some people might think this is a broken mechanic. Blizzard could put a stop to this quickly by dropping the range on mass res (currently 100 yards) or adding some kind of line of sight requirement since most res skips rely on ressing through walls or other obstacles. Also if
Пилон для обнаружения проблем wasn't an option in M+ it would severely crimp intentional death strategies.
Other skips generally start getting pretty questionable. Warlock's
Демонические врата has found a lot of use in M+ as a way to move between two points that would otherwise be untraversable. Typically the Z-axis is involved in these skips and they allow the group to get to a spot that probably wasn't intended. Blizzard has fixed some of these Gateway skips which gives some indication about how they feel about the skips in question.
One interesting thing to note when using the term “exploiting” is that Blizzard has not yet to my knowledge banned anyone for any M+ related activities regardless of how blatant some of the “exploits” were. The most recent example is Ularogg in
Neltharion's Lair. There was a taunt strategy that allowed you to prevent Ularogg from ever going underground for
Горная стойка so that the fight became a tank-n-spank with no intermission. This is quite obviously not how the fight is supposed to work and you had to go through some very deliberate steps to keep Ularogg from going underground. Most top groups used this method because it was necessary to post competitive times. Blizzard has since fixed it, and nothing was done to discourage the activity.
Blizzard appears to be a lot more willing to let players push up against the line between “exploit” and “clever use of game mechanics” in M+ than in raids.