Since you can specify that stats for leveling up (eg, you might want it to gain a 1.25x multiplier for attack after 8 kills), the old system (1.5x hp, 1.5x ep, 1.2x sight, 1.5x armor) is should generally not be used if you are specifying custom levels. Because of the large number of mods which may depend on this "faulty" combination of both the default and their specified custom leveling, we cannot just disable the old system when specifying which stats to raise and by how much when leveling.
I propose a new tag such as <disable-default-levels value="true" /> as a child for the <level> tag (sibling to the static-modifier and multiplier tags). If true, the default leveling will NOT take place. If false, it will take place in addition to whatever you specify, unless you override them with:
<multipliers>
<max-hp value="1" />
<max-ep value="1" />
<sight value="1" />
<armor value="1" />
</multipliers>
As it is, if you wish to disable to default system, you must specify this multiplier above, as it will override the defaults then. The implementation of a <disable-default-levels value="true" /> tag would be a cleaner alternative to disable to default levels, as well as hopefully reduce the number of modders who may be surprised to find the default is combined with their custom chosen stat increases.