Water-9 Blessing quickness is 50% Heroic quickness, not Magical quickness. Magical quickness gives +3 att / +3 def and 2X attacks / moves; Heroic quickness only gives increased increased attacks and moves. The two are multiplicative. Water-9 itself gives +4 def, of course, so a Water-9 blessed unit with Boots of Quickness would have +3 attack and +7 defense, and 1.5 * 2 = 3X normal movement. That makes the unit very strong
Be wary of quickness. It is not good for high-encumbrance units, since they tire at double (or 1.5x) the normal rate. Earth-blessing does not help much, since reinvigoration is not affected by quickness. Life-draining attacks solve the problem. In other words, do not give quickness to a supercombattant with 6 encumbrance and 6 reinvigoration, or it will pass out eventually (gaining 6 fatigue per round).