Quote from: Blizzard (Source)

We want to provide some information about the direction of the Arena system. Upon the release of Wrath of the Lich King, players will find they are still able to access the Arena system at level 70 for rated matches. Those competing in the Arenas at 70 will still be able to attain items using Arena points and rankings; however, we do not currently plan to offer new items or titles for this bracket. Players who level past 70 will have their Arena points reset to 0 and be removed from all Arena teams in the level-70 bracket.

Two new skirmish brackets (71-75, 76-80) will be available for players who wish to hone their Arena skills while leveling in Northrend. Those who reach level 80 will once again have the opportunity to create new Arena teams and play in rated matches once a new season starts. New items, titles, and end-of-season rewards will be offered to the most successful teams at level 80. Additionally, the sets released for the Arenas in Wrath of the Lich King will no longer share aesthetic similarities with tiered raiding gear. We want those equipped with the best PvP rewards and those with the best raiding sets to stand out from each other. Players at level 80 will also have the opportunity to compete in two new Arenas featuring challenging new layouts, terrain hazards, and moving obstacles.

Quote from: Blizzard (Source)

This is not a bug.

In the latest WotLK beta push, we made a large change to the mana cost of spells. All player spells now cost a percentage of base mana rather than a fixed cost. Base mana is a special value determined by the player’s level and class, regardless of any effects or items that increase intellect. It is the size of a player’s mana pool if the player has zero intellect.

This change was made primarily to prevent downranking, as it’s a technique that was never quite intended. Rather than continue to find ways to penalize players for casting low-rank spells, we decided to essentially make doing so obsolete. If rank 5 and rank 6 of a spell cost the same amount of mana, but rank 6 does more damage/healing, then there is no reason to consider casting rank 5.

So, each spell line (eg. Frostbolt, Shadowbolt, Greater Heal, Rejuvenation, etc.) has a fixed percentage of base mana that it costs for most of its ranks. That means each time a player gains a level the cost will go up some. The percentages were picked to attempt to keep the costs relatively similar to what they are currently in World of Warcraft. For most spells, that percentage will drop some when the player receives their highest-rank spell in existing Burning Crusade content. This was done to better fit the existing cost curve, and to keep the mana cost for level 70 players as close as possible to existing costs. Level 70 characters will see most of their maximum rank spells change in cost slightly up or down, but not by significant amounts.

We anticipate there being some balance concerns due to this change, and our development staff will be ready to implement new spells, abilities, or talents to resolve those issues as the testing process continues.