What exactly are you upset about? They've literally been doing this for years. Only thing new is the higher progressive odds, compared to what was before just x10.

I've had no luck with it yet, done 122 shards and haven't pulled  a champ I've selected. RNG is a bitch.

I would agree. How is it possible that between the progressive chance, and the mercy system, that I didn't pull Siphi with 240 void shards. Or even a Lego. From Content creators I saw this event was on the horizon, and held all my void shards. I've been banking them forever just waiting for a Siphi opportunity. Blew them all....and I have like 8 skullcrowns, a million Weregren and Nia's, but not a Siphi or Lego.

The simple answer to your question is - math. This isn't a 2x event, so your odds for a lego on void shards is 0.5%. From 240 pulls, the chance you didn't get a lego is simply (1 - 0.005)^240 ~= 30%. Or, put another way, roughly one in three people who pull 240 void shards will receive nothing but a pile of rares, epics, and irritation. C'est la vie.

PS - as for the mercy system, that only kicks in at 200+. You get +5% per pull from 200 onwards. Now, given that 0.05 * 40 = 2, aka a number greater than 1, your math simply does not compute. IE, you did not open 240 void shards and receive only epics and rares, and, if you did, you should open a support ticket.

I expect more likely is you did in fact get a lego from those 240, and unfortunately it is one of the many non-memorable ones, and you simply forgot about it.

What are the actual odds on Acelin the Stalwart.  2x plus 10x progressive.  

And is Acelin worth the effort?  

1% chance of getting a lego from blues on a 2x, so to have a ~50% chance of getting a lego, you'd need to use Ln (0.5) / Ln(0.99) ~= 69 blue shards. If you get a lego, there are roughly 250 in total, of which roughly 70 are void, leaving about 180 non-void. So your odds of getting Acelin on a 10x are ~10/180 ~= 5.5%.

So, simplistically speaking, you'd need somewhere around 700 blue shards to have a coinflip chance of getting him.

Wish more people knew the actual numbers you just posted krama, their 10x system is really misleading to average joe, its like reading only the headline of news article :P