At every top (that was last week), the market has to go higher or none of us should be investing. And the market should spend most of its time at or near a top, so the degree of topiness should not impinge on how one invests.
That written, if I was DCA'ing a lump sum, I would put 50% in now and the rest as 5% monthly increments so that all would invested within 10 months. I would also have a written plan to accelerate DCAing if the market dropped in those 10 months.
Is that a reasonable alternative?