With the current difficulty there is a disconnect between what is intended and how the game actually plays. As it stands now, there is currently no content in the game that actually requires that the Tanker class be played whatsoever, as nothing deals enough damage. This includes enemies with specialized ways of dealing damage, such as the Hamidon. There is also no need for dedicated healing at all, such as the Pain and Empathy powersets, as nothing deals enough damage. Specifically with the SCoRE changes to Blasters, there is nothing really to stop a player from single-handedly steamrolling through all of the games content on a ranged DPS'er, as they have access now to an undue amount of survivability that eliminates any challenge to staying alive they might face. There is also very little in the way of enemies that have enough HP and damage output that actually requires a team. Both the Hamidon and Really Hard Way Tyrant are somewhat easily disposed of with merely 4 players, despite being challenges intended for very large groups of players. While certainly not everyone is going to be able to pull this off, the fact that it is even possible in terms of numbers suggests a large gap between how powerful player characters are expected to be and how powerful they currently are. In particular, the Destiny slot stands out as particularly broken as a mechanic, with the values for returns on virtually every destiny being much too high for literally every person in a team or league having them.
Additionally, economic and character progression changes have trivialized access to the power ceiling for any given character. Being able to obtain normal rewards in AE, incarnate xp from all content, gaining immense rewards simply by leveling via veteran levels, and having prices cut on all very rare/end game items at both merit vendors and on the auction house reduce the effort needed to bring a character to the point where the game is trivially easy. While the item economy is preferable to what was available on live, the ability to fully equip a character with tier 3 incarnates in every slot 2 hours after freshly rolling the character via AE farming is excessive.
A good difficulty change would force players to actually need to use mechanics found in other RPG style games, such as aggro management or focused targeting, while still allowing the level of build diversity that characters enjoy in CoH, without being able to fully max out your character shortly after rolling them.