T2 is so much better than T1, even without the online addition.
The art direction gets a minus, although it pleases at times, when it comes to explosions and color, it otherwise looks quite dated, in a Warcraft 3 style/way that is quite obvious. It gets better as you level up and start donning cool looking armor and weapons, but the lack of detail up-close disappoints. The story and characters are also forgettable, but tolerable, as you chase the trail of "the Alchemist" through the lands, and help the locals you meet along the way.
The UI and inventory are all smooth and take a little time to learn properly, as does the skill system and weapon/armor/trinket types, just how I like it, deep enough to be thoroughly engaging, creating a slower, more Diablo 2-like pace, yet you're constantly progressing and shaping your character every level, moving swiftly through dungeons, only to stop and inspect loot or send your pet into town with its shopping list and inventory to clear - a brilliant system from T1. This isn't the auto-pilot game Diablo 3 is, but appeals to those who loved Diablo 2 so much.
The game is relatively bug-free, runs smoothly, and is one of the best ARPG's ever made, simply by taking a proven formula, and expanding, improving and modifying it to be a better experience.