Grounded (3) is an upgrade from Grounded (1) in all of the ways the other Composures have been upgraded, but also note that the single icon on the level 1 is now ! We have a few cards that care about icons on cards that you don't really want to throw into the discard pile now, notably Well Prepared and Astronomical Atlas. Grounded joins a select few assets that have : quite a few signature cards, but also Prophesiae Profana, the two Precious Mementos, The Black Cat and The Red Clock (5). Grounded at level 3, fast, and 0 resources is the most easily accessible of the bunch so far.
Diana Stanley can take Well Prepared and Astronomical Atlas (though not sure she wants it), and loves the boost on whatever skill she is testing, since she will often test all of her skills. Diana/Well Prepared/Physical Training (2) is already a great combo, but remember that cards like Read the Signs actually are tests, so Grounded (3) does give you a boost there too, both on the wild icons for Well Prepared and the +1 skill boost. Finally, note that using Well Prepared for the icons here makes up for the fact that you can't use its boost on treachery cards, a notable downside already mentioned compared to Holy Rosary.