It's a combat spell because you have to go right up to the target, chant magic words at it, wave your hands around, and poke it. And then it starts making saving throws at the end of its next turn, so it knows whatever you did was nasty. It's about as subtle as a warhammer to the face.
As for the duration being a week--so what? What is that going to do for you? It's not like you can cast it from safety and wait for it to take effect. The touch range means you have to expose yourself to retaliation. And the fact that you have to make an attack roll and the target has to fail a saving throw makes it very difficult to concoct plans around--what if you miss, or the target makes its saves? What if there's a 3rd-level cleric, druid, or bard in the house... or, for that matter, a 5th-level paladin or ranger? Lesser restoration is only 2nd level, and it's a very popular spell.
The only value I can see in "no effect till 3 failed saves" contagion is that, if the DM rules it's infectious, a wizard of less than sterling moral character can cast it on some helpless schmuck and start a plague. But the text doesn't even mention the possibility of infecting others, which makes it very hard to argue that was the intended use.