As the title states time-limited ECs are a terrible idea without the rework. By rework I mean the update KR recently did that allows you to 'roll back' using BP if you don't like what you rolled.
Because of how costly rolling gear for a good 3rd line is (4 ECs per roll) people need to stack as many ECs as possible before attempting to re-roll to avoid running out of ECs before getting a better roll than they previously had (and thus leaving them worse-off). So for example with our current event only 20 of these ECs in the event shop means only 5 rolls with 2 lines locked. Odds are you're more likely to blow through these 20 (5 attempts) and end up with a bad 3rd line than getting the line you wanted. At least with the rework you can use BP to avoid ending up worse-off in the end. Being time-limited means you are basically forcing people to use them in a way that is likely to do more harm than good to their gear.
That said, even with the rework, time-limited ECs are just a bad mechanic. There is no reason they should be time limited. If you want event ECs to be soulbound then fine, make them uniques like the ones crafted with EC parts (and don't touch the legendaries as it's important to be able to buy/sell them on the market too).
Also EC drop rate in general is bad. Almost impossible to get them in IDD and dismantling AOV gear has terrible rates as well. Considering how costly rolling gear is these rates really need to be buffed a bit.
