Like what problems are you referring to exactly?
Are you saying that changing a number fro 7.000 to 10.000 could eventually create bugs? Or that it could lead to eventually over-buffing something?
Because for over-buffing, you still can do the math preemptively and come to a reasonable conclusion in most cases, and in regards to introducing a bug into the game, I do not see how changing the values for damage, defense, resource costs, cooldowns, etc can introduce a bug.
The main testing at this moment in time is done for the season themes and of course you wanna test that before introducing it to the live servers.
However, for the numerical values of sets and legendaries this is a bit different I would argue (at least I think it is - from a layman’s perspective). You still can do the math to predict an outcome of how builds will preform, which is not rocket science.
Many people on the forum already have done calculations on what to buff and nerf by how much to create more balance.
Furthermore, in regards to mechanical changes to Skills like Teleport, I also do not think that it would be that difficult to replace the Cooldown on Teleport with either 2 or 3 Charges or to give Teleport Resource Costs.
For Charges you could simply copy and paste the numbers of Dashing Strike and put them into Teleport in the data row that determines the amount of Charges and their Replenishing Time, while removing the number from the row that determines if a skill has a Cooldown and how long that Cooldown would be.
I don’t know how their spreadsheets look like, but according to an interview that Jay Wilson gave in which he said that all skills have different spreadsheets for PvP and PvE and that they easily can change some values, I assume that this is rather an easy thing to do.
This is just me as a layman talking, but I would be really surprised if Blizzard would not have a program or a way that allows them to make these numerical changes easily.