Some mistakes I've noticed in the first video:
-v'tar orbs cannot give you life, but they can remove damage.
-v'tar orbs CAN be turned back to neutral after the sslak guarding it is dead. It takes two melee attacks to steal an orb that your opponent controls: one to turn it back to neutral, and another to turn it to your control.
-a 5x20 arena is not possible unless you buy 5 copies of the expansion. There are only 20 tiles in the expansion.
-corrode pool does not do direct damage. Corrode pool deals a corrode condition to each non-flying corporeal creature in its zone. A corrode condition lowers a creature's or conjuration's armor by 1. If a creature or conjuration that has no armor receives a corrode condition, the condition immediately falls off and deals 1 damage to that creature or conjuration (since armor cannot be below 0)
-5x4 is only one possible configuration for an arena using tile zones in the domination expansion, since the tile zones are separate pieces. They don't actually come as a 5x4 arena. In fact, 5x4 isn't mentioned anywhere in the rules. The actual example 2v2 arena that is shown in the rulebook is shaped quite differently. It has 14 zones total: 2x6 with two zones added near the bottom left side and near the top right side, with a secret passage connecting them.