Some of my suggestions include:
Power Spell
Dark Power
Force Spell
Fury Spell
Damage Spell
Temper Spell
Adrenalin Spell
Strategy would include better use of any set group of troops. Wizards, barbs archers giants goblins, any group...
The spell would allow a group of troops to destroy targets faster with out the help of speed. As where Haste and rage moves troops through an area quicker. This set spell gives you the option to take down storages TH'S or the castle faster with out rushing to the next target and becoming venerable by surpassing the tank units.
Attacks are generally planed out to try to keep the tanking units a head of the pack despite their lack of speed. (Hogs are not very tank like, they have a weakness) . However rage and haste move the already faster units ahead of the tanks into bad or worsening positioning.
I don't even have haste yet but I know by tactical instinct ,I guess you could call it, that this will be downside of using haste. As well as it is using rage but rage allows my giants to be stronger (if placed correctly😠😡

as well as faster! Haste is just faster with no added strength. Power wi'll be strength with no added speed. Downside, I mean does it need a downside?
FOR THE SAKE OF OP
For the sake of op the spell only lasts 3 seconds at lv1, 5 sec. lv2, and 7 sec. lv3.
Side note* in life we are faced with situations that call for the supernatural ability in ones self to accomplish feats of speed or strength without hesitation.
These" feats" are categorized as bursts of adrenalin. This is normally speed and strength
But for the purposes of spell casting or potion brewing in this game, we be able to choose. Power or Speed?