...wouldn't there be a lot of multi colored decks due to Invasion?
YES, there will be.
Rishadan Port - Will effect the environment SO MUCH, since it could bascially, and easily, ruin all those Multi decks.
Dust Bowl - Just like the Port, this will be used heavily.
Wintermoon Mesa - I could see this coming into play. It's not that hard to imagen now, with the slow environment, this card could be a Multi deck's nightmare.
AND ONE MORE CARD EVERYONE FORGOT TO MENTION:
TANGLE WIRE - The scarry part is that any deck could run 4 of these, just like all the lands above, but THIS is much more effective, and IT WILL SCREW some decks all over and IT WILL SLOW DOWN THE ENVIRONMENT even more. I could see Blue Control and Black/Blue control decks running 4 Wires each, since they slow the game down even slower than it is, AND since Blue has ACC Counterspells, it doesn't have to worry SHOULD the opponent manages to get ANYTHING DANGEROUS earily.
IF you look above, you'd see three lands. Three non-basic lands that will likely rule the T2 scene. WHAT card is most effective against all these? UM, how about that Web artifact from Invasion?
It stops ALL OF THEM, AND GIVES YOU A CARD! HOW ABOUT THAT!