Nerf Eldrazi in Historic
Wizards of the Coast repeatedly talked about how they try to "cure" Historic in three ways:
1) keeping fast mana out of the format;
2) limiting land hate;
3) not permitting free spells in historic.
Well, Eldrazi decks explicitly broke the first two points:
1) They have access to 2 different "sol lands", Eldrazi Temple and Ugin's Labyrinth, which allow them (and only them) to access free mana in the first turns to speed up their game plan;
2) They have Sowing Mycospaw (a card banned in legacy) to ramp themselves (and only them), looking for the lands listed in point one, and to slow down their opponents. That usually happens in turn three, destroying every possible other strategy in opponents' decks. Since it is an ability that triggers on the cast, it isn't easy to interact with if you don't have the exact response. Therefore, everyone is obliged to hard-mulligan in order to search for a single card. That's unfair, as you can comprehend. Worst of all, this card ramps while destroying opponents' lands, creating a great disadvantage.
In conclusion, it's clear that this deck plays another format, and if you play the format, it' very clear that Eldrazi decks have n necessity to interact with other decks. They just go on playing their own solitaire.