I'm not sure about difficulty, but I'm aware that the structure is very different. Raids in XIV are simply glorified trial instances. Deltascape in particular seems to have been tuned fairly easy by the games own standards, though savage is far more challenging than normal mode and requires group co-ordination and a good understanding of the game mechanics.

As for soloing raids, coil is definately soloable these days but I'm not sure if Alexander is.