Flasks and Life/Mana are not restored upon entering town or your hideout. Vendors that sell Flasks (and Helena in your hideout) can refill them for you. This disincentivises the strategy of using Portal Scrolls as an instant full heal.
Onslaught does not grant movement speed in Ruthless. This relates to the absence of movement skills.
If you die near a quest boss in the campaign, a chunk of its life is recovered.
Utility Flasks can not gain charges while active and have lower duration than they do in regular Path of Exile.