Getting multiple OHLCV candles with API with one request
You can do this with ClueDex. By default, all Bittrex markets are returned in a single query. You can specify how many candle data you wish to get with the "periodqty" parameter. In your case, you make periodqty equal to 1 for the last period. 

Additionally, you can create your own period, you aren't limited to the standard periods. For example, if you wanted 30-second periods, you just specify the "period" parameter as 30S. 

If you had a need to go back in time Cluedex also has the capability to do that, too. 

The only drawback is, if it even is one, is that it's not a free API, it's premium. However, the prices are reasonable and the data isn't cached.