My mistake on the PVP and SDI, this will not go above cap I had thought the question was about PVM.
All of my information is from running my own bard and questions I have placed or read on stratics and then confirmed after.
I have casted invis many times on my guy and does break the line of sight that a monster uses to lock onto your char. When you have the peacemaking spells cast it will auto reveal you though.
You cannot go over the hard cap of 25HPI from the Invigorate spell.
At 480 real skill you will get 11 mana regen, hpr and stam regen for your party. Poison cures at the same time rate as vampiric embrace, as does curse reduction and bleeding.
I don't often cast Perseverance as I cannot keep both this and Resilience going for long on my bard(I only really use this spell stuff for soloing corgul and found Resilience the best spell to cast). At 40 LMC and 20+ mana regen I could keep both spells going for a long time but I cannot cast heal on my wammy for long so I just leave the Peresvarance alone due to the mana cost of both spells and healing. My bard is 480 barding, 120 med, 110 magery and what ever was left over into focus.