In wide column tables I have found batch get very useful for larger number of operations. As for now there is no other way than constructing QueryCondition containing a lot of .or().is().is()....close(). If you go this way, than you won't know which document IDs from the input were not in the table (would return null) without doing some extra logic on the retrieved documents (e.g. putting in a set).
I suggest to have something which would replace HTable.get(List<Get> gets), so you do not need to call Table.findById() in a cycle for each ID separately.
More described in my Batch operations on a JSON table question.