I gave the DLC campaign a serious try for the first time and I can say that, despite the simplicity and straightforwardness imposed by 5E, the game now has enough classes and archetypes to allow a bit of creativity in building your party. My current party is: fighter (commander), ranger (swift blade), wizard (court mage), and sorcerer (haunted soul), and I have been positively impressed by the amount of interesting interactions that can come up between these classes.
For example, the Commander archetype works well with the Haunted Soul, since the free spammable advantage given by Rousing Shout allows the Sorcerer to reliably hit his Twinned Inflict Wounds. Inflict Wounds deals massive damage, but I usually avoid it due to its unreliability: this combination greatly improves its effectiveness, allowing you to deal 20-30 damage to 2 targets at level 3.
However, using Inflict Wounds puts the Sorcerer in a dangerous position in melee range... which isn't really a problem thanks to the Court Mage's Spell Shield and Protection fighting style. Spell Shield might be a bit broken, though... between this and the Shock Arcanist it's clear someone at Tactical Adventures really likes Wizards (is it you,
Myzzrym?). Anyway, Spell Shield also offsets the biggest flaw of this party composition (the lack of Healing Word).
But my favorite interaction so far has been that between the Sorcerer's Twinned Haste and two melee fighters that heavily benefit from having more attacks. At level 5, giving Haste both to a fighter with a greatsword and a ranger with Hunter's Mark is bonkers. With Action Surge and Follow Up Strike, the Fighter can spam 6 attacks in a round, while the Ranger fighting with two weapons 4, which is great for Hunter's Mark and becomes absurd at level 7 with Battle Focus.
tl;dr: the game is still simple and straightforward, but the new classes and subclasses add a lot. The upcoming updates can only make things even better with bards, warlocks, and (sigh) monks.