Disagree with a fair bit of that. Getting the event girls, yes. Getting the elite, no. That last part should require cores (whether by cash or other work is irrelevant).
There is no standard in games that it should cough up the perfected version of an event unit in existence.
A few games do it, loads of others do not.
RNG will always be a factor in these games, the whim of "luck" drives consumption as it does in all types of gaming in the world, the extra roll, the chance of scoring big etc. But there is a fine line between RNG and too much RNG in games, agreed. But less RNG means more demand for cores to be put in, thats the trade off.