Hard to disagree with the majority of members posting here, as they are correct that swords sampire is the optimal pvm dexer template, at least in terms of versatility and survivability. They are especially good with large groups of mobs (whirlwind) and also very effective against single targets (ai/onslaught+dbl strike)... So if you are new or newly returning that is the best option for you. If cost is an issue mace fighting can also make a good sampire, at least until you can afford that rather pricey 120 swords PS.
However if you want fun or a challenge there are a number of alternatives available to you, many listed here. Pure pallys (enjoy your 4/6 casting and the benefits of using a shield), dragoons (basically samp with healing instead of necro), ninja dexers, and all types of archers and tamers... Even melee tamers and tamer/archers, ofc!
UO is still a great game with a lot of room for cross-classing. Even the cookie-cuttingest sampire template will call for a swap of anat/lumberjack/resist from time to time! But you must realize the game has evolved into a more equipment-oriented play style, and with equipment optimization comes skill optimization. But don't feel forced to play a sampire to be viable in pvm, just take the kernel of wisdom that it does come heavily recommended with a grain of salt, and play the game however you'd like.
If you are the min/maxer type that must have optimized survivability and damage output, you should give it a shot. but then again if you were that type of player, i wouldn't have felt the need to write this long ass post and conclude it by telling you so! Is it more fun to play a quirky template, or more fun to rest-assured knowing you are optimally efficient?