Lesson 2: The Dispenser and Teleporter are really good. We already knew this, but we didn't know that they were really, really good. Encouraging Engineers to either avoid building them entirely, or to build them in weird ways, broke the game's pacing immediately. New buildings in the Engineer update will probably take the form of upgrades, or entirely new choices alongside the old buildings, instead of replacements.
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Ultimately, the Repair Node was cut because it made the game more of a grind. While it definitely made it less stressful to manage a base as an Engineer, it wasn't fun. The Engineer gained a little bit of fun, but nearly everyone else in the match suffered as a result.