I played mtgo years ago (lorwyn was last set) and it wasn't on par with this, opening hands were worse in mtgo. But eternal has it beat in the drawing department, I've never come close to the amount of mana screw/flood in mtgo that eternal provides.
It's not the shuffler, it's the 75 card deck size. It increases the chances of drawing 'clumps' of power or non-power cards in a row. I got involved in a huge debate about it on the beta forums, even had some math guys run some simulations that showed the issue.
Simplest way to think of it is to compare a 10 card vs 100 card deck, with a 50% power to non-power card split for simplicity.
If you have 10 cards, and draw a power first, it's now 4 to 5 chance to draw a 2nd power in a row. If you draw that 2nd in a row, it's now 3 to 5, etc..
in a 100 card deck, if you draw a power, it's 49 to 50 to draw a 2nd one. If you draw a 2nd one, it's 48 to 50. Each individual power drawn doesn't reduce the chance to draw the next one by very much in a larger deck.
Same thing in going from 60 to 75, just less drastic. But, when you have that extra 1% (or whatever it is) chance every draw step, in every game, it leads to more mana screw/flood situations then you are used to. Sure, the opening hand is weighted to be good, but the chance your draws after that are all the same card type is higher in a 75 card deck. This is why I thought they needed more library manipulation effects in the game.