I'm late to the game on this, but I have one comment on teleport slotting.
Slotting range enhancements will give you better speed, but slotting end reducers will give you better distance per endurance.
The guide is entirely correct in saying that endurance reducers yield diminishing returns, but that only concerns endurance use per unit of time. However, the affect on the distance you can TP is linear.
Using the figure of 15 end per hop, 3 +0 SO end reducers will bring your end use to 7.5 a hop, and 6+0 SO end reducers will bring your end use to 5 a hop. In short, you "gain" 7.5 end per hop with the first 3 enhancments and only 2.5 en per hop for the other three.
However, if we want to think about total distance, we need to think about number of hops you can do before running out of end. For simplicity, I'll assume 300 end and no recharge. (I use 300 becuase it divides evenly in all cases, and thus shows the linear relationship most clearly.)
At base, you could do 300 / 15 ~ 20 hops
With 3 +0 SO's, you could do 300/7.5 ~ 40 hops
With 6 +0 SO's, you could do 300/5 ~ 60 hops
Since the length of the hops don't change with the number of end reducers used, the total distance you can travel on a given amount of endurance is determined only by the total number of hops. As the listing above shows, the second 3 SO's yield the same increase in the number of hops (over 3 SO's) as one gets by going from no SO's to 3 SO's. The maximum benefit from (even level) SO end reducers is then a tripling of the distance you can travel.
For comparison, range enhancements boost the distance you can travel (for a given amount of end) by increasing the length of your hops, rather than by increasing the number of hops you can take before being exhausted. Since the time spent hopping does not seem to vary with the dstance being hopped, range enhancements also boost speed. However, range enhancements have a weaker affect on the total distance you can travel than endurance enhancments do, allowing yo to (at maximum) go 2.2 times as far as you could with unslotted teleport (vs 3 times as far with endurance enhancements).
For many, range enhancers are probably still better, since they reduce the time spent travelling as well as increasing the distance one can travel. However, someone less concerned with speed and more concerned with continuous motion toward an objective may prefer the endurance reducers.
