MTG Duels of the Planeswalkers – Playing Coop Games on Steam

I had problems with that challenge too. Here's the solution on Youtube. I hope it helps.

Banding is not currently used in the 2011 rule set for Magic: the Gathering. While the current blocking rules may seem similar to Banding, the big difference between them is that Banding considered blocked creatures to be one creature. The current blocking rules treat every creature as an individual, as was the case when Banding was still an active keyword. Note the sentence "As usual per normal rules, you can always block 1 creature with any number of creatures..." in the Wikia article.

This link provides a listing of resources for the basic and comprehensive rulesets for the 2011 Core Set (aka the current version of the rules).

A basic form of the current blocking rules are as follows:

An attacking creature that is blocked deals damage to the blocking creatures. If one of your attacking creatures is blocked by multiple creatures, you decide how to divide its combat damage among them. You must assign at least enough damage to the fi rst blocking creature in line to destroy it before you can assign damage to the next one in line, and so on.

You can find the full details of the current Blocking rules in section 509 of the Comprehensive Ruleset, a small, relevant section of which I have quoted:

509.2. Second, for each attacking creature that’s become blocked, the active player announces that creature’s damage assignment order, which consists of the creatures blocking it in an order of that player’s choice. (During the combat damage step, an attacking creature can’t assign combat damage to a creature that’s blocking it unless each creature ahead of that blocking creature in its order is assigned lethal damage.) This turn-based action doesn’t use the stack.

Example: Craw Wurm is blocked by Llanowar Elves, Runeclaw Bear, and Serra Angel. The Craw Wurm’s controller announces the Craw Wurm’s damage assignment order as Serra Angel, then Runeclaw Bear, then Llanowar Elves.

509.3. Third, for each blocking creature, the defending player announces that creature’s damage assignment order, which consists of the creatures it’s blocking in an order of that player’s choice. (During the combat damage step, a blocking creature can’t assign combat damage to a creature it’s blocking unless each creature ahead of that blocked creature in its order is assigned lethal damage.) This turn-based action doesn’t use the stack.

I don't know when the last time you played was, but there were also several changes made in 2010 that may also affect your understanding of the current blocking rules, the most important of which is that combat damage no longer uses the stack. These changes are detailed in this article. Scroll down to section 5, which also uses examples which should help your understanding of the current state of the game. While it is different to the rules you may be used to, I would disagree with calling it "exploitation," especially as the game is programmed in such a way that blatantly abusing/ignoring the rules isn't really possible.