Rift mage vs dragons/giants?

The dragon fights are very situational and would require switching a few abilities from the bar anyhow - one can't really do much damage with fire damage to a dragon that breathes fire, or lightning dragon with lightning spells or frost dragons with frost spells. Some fights are also different from some others (like in case of dragon in Crestwood) because at some point some dragons with spawn dragonlings and those can be pretty nasty if not taken care of. CC rift mage abilities work best on adds - the main one that works for everything is Stonefist - the Unblockable Force morph is good for stages of fight in which the dragon generates guard for itself.

The rest really depends on party composition, coordination, gear and healing supplies - is there a barrier on your bar or is there mage throwing a barrier, or do you have guard-generating equipment or how many healing potions you have. I highly recommend upgrading Regeneration potion as high as you can, because that thing can be invaluable during tough fights. You'd probably have to feed most of those to (and keep barrier on) your tank and micromanage the fight a little for the tank to keep the attention of the dragon. That allows for others to apply damage without being smashed around. I you have Healing Mist potion, it can be very useful too if it's equipped on at least one companion.

Also - dispel. That ability can be really helpful during fights, when the dragon applies effects on people. Also, it will trigger combo from mines if you manage to put it on a dragon (fairly sure it will mostly affect its feet, maybe tail). Oh and revive, lower level fights will benefit from that.

Is the firestorm not a good spell?