Have a greater variety in focus costs and have some runes be 200 or more. This will encourage players to invest in focus as a stat more if the really good runes are locked. Have runes that cost 50 have basic attack damage and higher cost runes have increased damage of 20% more damage per 50 cost above the 50 benchmark.
Remove focus gain on focus use. Change this to either increase focus gain on non-focus damage to prevent focus spamming or to decrease in focus cost as that is the basic end result without allowing unlimited focus spam.
Allow INT to increase focus damage either as a percentage or flat bonus.